Prevention of postoperative pericardial adhesions using tissue-protective solutions

Fibrin Hydrogel Layer-Anchored Pericardial Matrix Prevents Epicardial Adhesion in the Severe Heart Adhesion-Induced Miniature Pig Model

Postoperative adhesion is a very common and serious complication that occurs frequently in cardiac surgery. The purpose of this study was to evaluate the efficacy of a fibrin hydrogel layer-anchored decellularized pericardial matrix in preventing pericardial adhesions in a miniature pig model with a myocardial injury. Fibrin hydrogel layer-anchored decellularized pericardial matrix was prepared by spraying a mixture of fibrinogen and thrombin on a fibrinogen-doped decellularized pericardium. Cardiac injury was generated by abrading and desiccating the epicardial surface of a miniature pig to induce severe postoperative adhesions. The adhesion between the epicardial surface and fibrin hydrogel layer-anchored decellularized pericardial matrix in three different regions (left outer, front, and right outer) was evaluated macroscopically one month after surgery. The fibrin hydrogel layer-anchored decellularized pericardial matrix showed significantly less adhesion than an autologous pericardium (0.2 ± 0.7 in DPM-FHG0.5 and 0.4 ± 0.8 in DPM-FHG1, p < 0.01) and expanded polytetrafluoroethylene (ePTFE) (1.6 ± 0.5, p < 0.05). The fibrin hydrogel concentration had no effect on preventing postoperative adhesion. A thinner fibrin hydrogel layer was observed on the decellularized pericardial matrix one month after surgery; however, the inside of the matrix was filled with fibrin hydrogel. Fibrin hydrogel layer-anchored decellularized pericardial matrix prevented postoperative epicardial adhesions in a miniature pig model. Our findings suggest that pericardial closure using a fibrin hydrogel layer-anchored decellularized pericardial matrix is a promising method for preventing adverse outcomes in reoperative surgeries.

A review of animal models for post-operative pericardial adhesions

Post-operative pericardial adhesions remain a serious complication after cardiac surgery that can lead to increased morbidity and mortality. Fibrous adhesions can destroy tissue planes leading to injury of surrounding vasculature, lengthening of operation time, and increased healthcare costs. While animal models are necessary for studying the formation and prevention of post-operative pericardial adhesions, a standardized animal model for inducing post-operative pericardial adhesions has not yet been established. In order to address this barrier to progress, an analysis of the literature on animal models for post-operative pericardial adhesions was performed. The animal model, method used to induce adhesions, and the time to allow development of adhesions were analyzed. Our analysis found that introduction of autologous blood into the pericardial cavity in addition to physical abrasion of the epicardium caused more severe adhesion formation in comparison to abrasion alone or abrasion with desiccation (vs. abrasion alone p = 0.0002; vs. abrasion and desiccation p = 0.0184). The most common time frame allowed for adhesion formation was 2 weeks, with the shortest time being 10 days and the longest being 12 months. Finally, we found that the difference in adhesion severity in all animal species was similar, suggesting the major determinants for the choice of model are animal size, animal cost, and the availability of research tools in the particular model. This survey of the literature provides a rational guide for researchers to select the appropriate adhesion induction modality, animal model, and time allowed for the development of adhesions.

Prevention of postoperative adhesion with a colloidal gel based on decyl group-modified Alaska pollock gelatin microparticles

Postoperative adhesion, bonding of the abdominal wall to damaged organs, causes severe complications after abdominal surgery. Despite the availability of physical barriers (i.e., solutions, films, and hydrogels), adhesion prevention materials that are a single-substance system with stability in wet tissue and ease of use have not been reported. Here, we report a microparticle based, sprayable adhesion prevention material comprising decyl group modified Alaska pollock gelatin (C10-ApGltn). C10-ApGltn microparticles (C10-MPs) were prepared by a coacervation method, freeze drying, and thermal crosslinking. The C10-MPs adhered to and formed a colloidal gel layer on intestinal serosal tissue by hydration without any crosslinking agents. After hydration of the C10-MPs, the resulting colloidal gel layer did not adhere to other tissues. Additionally, the C10-MP colloidal gel layer formed on the stomach serosal tissue showed stability when submersed in saline for 2 days. The colloidal gel layer also showed tissue followability. An in vivo rat adhesion model revealed that C10-MP colloidal gel layer on the cecum and abdominal wall defects effectively reduced postoperative adhesion and induced tissue remodeling, including re-mesothelialization. Therefore, C10-MPs are a potential anti-adhesion material for preventing postoperative adhesion. STATEMENT OF SIGNIFICANCE: We evaluated the postoperative adhesion prevention ability of a colloidal gel based on decyl group modified Alaska pollock gelatin (ApGltn) microparticles (C10-MPs). These microparticles are sprayable and form a colloidal gel with only hydration on the gastrointestinal tissue. We revealed that the modification of the decyl group into ApGltn improved the stability of C10-MP colloidal gel on the tissue by hydrophobic interaction in the in-vitro experiments. The gel prevented postoperative adhesion by being a physical barrier in the in-vivo rat adhesion model.

A functional PVA aerogel-based membrane obtaining sutureability through modified electrospinning technology and achieving promising anti-adhesion effect after cardiac surgery

Pericardial barrier destruction, inflammatory cell infiltration, and fibrous tissue hyperplasia, trigger adhesions after cardiac surgery. There are few anti-adhesion materials that are both functional and sutureable for pericardial reconstruction. Besides, a few studies have reported on the mechanism of preventing pericardial adhesion. Herein, a functional barrier membrane with sutureability was developed via a modified electrospinning method. It was composed of poly(l-lactide-co-caprolactone) (PLCL) nanofibers, poly(vinyl alcohol) (PVA) aerogel, and melatonin, named PPMT. The PPMT had a special microstructure manifested as a staggered arrangement of nanofibers on the surface and a layered macroporous aerogel structure in a cross-section. Besides providing the porosity and hydrophilicity obtained from PVA, the structure also had suitable mechanical properties for stitching due to the addition of PLCL nanofibers. Furthermore, it inhibited the proliferation of fibroblasts by suppressing the activation of Fas and P53, and achieved anti-inflammatory effects by affecting the activity of inflammatory cells and reducing the release of pro-inflammatory factors, such as interleukin 8 (IL-8) and tumor necrosis factor α (TNF-α). Finally, in vivo transplantation showed that it up-regulated the expression of matrix metalloproteinase-1 (MMP1) and tissue inhibitor of metalloproteinase-1 (TIMP1), and down-regulated the expression of Vinculin and transforming growth factor β (TGF-β) in the myocardium, thereby reducing the formation of adhesions. Collectively, these results demonstrate a great potential of PPMT membrane for practical application to anti-adhesion.

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A functional PVA aerogel-based membrane (PPMT) obtained sutureability through modified electrospinning technology.

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The primary mechanism to anti-adhesion of PPMT membrane was explored.

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Promising anti-adhesion effect of PPMT membrane was accomplished in pericardium reconstruction in rabbit.

Physically Cross-Linked Hyaluronan-Based Ultrasoft Cryogel Prepared by Freeze-Thaw Technique as a Barrier for Prevention of Postoperative Adhesions

Postsurgical peritoneal adhesions are a common and serious postoperative complication after various peritoneal surgeries, such as pelvic and abdominal surgery. Various studies have shown that peritoneal adhesions can be minimized or prevented by physical anti-adhesion barriers, including membranes, knits, and hydrogels. Hydrogels have attracted great attention in preventing peritoneal adhesions because the dimensional architecture of hydrogels is similar to that of the native extracellular matrix. However, chemical cross-linkers had to be used in the preparation of chemical hydrogels, which may have problems in cytotoxicity or unwanted side effects. This fact prompts us to create alternative cross-linking methods for the development of biocompatible hydrogels as physical barriers. Herein, we report a physically cross-linked flexible hyaluronan (HA) cryogel prepared via a freeze-thaw technique as a novel anti-adhesion biomaterial for completely preventing postsurgical peritoneal adhesions. In vitro studies demonstrated that this physically cross-linked HA cryogel exhibited excellent biocompatibility, the inherently desirable biocompatibility and functionality of HA being integrally retained as much as possible. Intriguingly, the rheological properties and appropriate biodegradability of the cryogels were readily tailored and tunable by way of the gelation process. In vivo assessments suggested that the cryogel, as a physical barrier, satisfactorily prevented fibroblast penetration and attachment between the injured tissues and nearby normal organs. Furthermore, the molecular mechanism studies revealed that the HA cryogel could prevent peritoneal adhesion by inhibiting inflammatory response and modulation of the fibrinolytic system. Our results show that HA ultrasoft cryogel is a promising clinical candidate for prolonged adhesion prevention.

Prevention of Post-Operative Adhesions: A Comprehensive Review of Present and Emerging Strategies

Post-operative adhesions affect patients undergoing all types of surgeries. They are associated with serious complications, including higher risk of morbidity and mortality. Given increased hospitalization, longer operative times, and longer length of hospital stay, post-surgical adhesions also pose a great financial burden. Although our knowledge of some of the underlying mechanisms driving adhesion formation has significantly improved over the past two decades, literature has yet to fully explain the pathogenesis and etiology of post-surgical adhesions. As a result, finding an ideal preventative strategy and leveraging appropriate tissue engineering strategies has proven to be difficult. Different products have been developed and enjoyed various levels of success along the translational tissue engineering research spectrum, but their clinical translation has been limited. Herein, we comprehensively review the agents and products that have been developed to mitigate post-operative adhesion formation. We also assess emerging strategies that aid in facilitating precision and personalized medicine to improve outcomes for patients and our healthcare system.

Preventing post-surgical cardiac adhesions with a catechol-functionalized oxime hydrogel

Post-surgical cardiac adhesions represent a significant problem during routine cardiothoracic procedures. This fibrous tissue can impair heart function and inhibit surgical access in reoperation procedures. Here, we propose a hydrogel barrier composed of oxime crosslinked poly(ethylene glycol) (PEG) with the inclusion of a catechol (Cat) group to improve retention on the heart for pericardial adhesion prevention. This three component system is comprised of aldehyde (Ald), aminooxy (AO), and Cat functionalized PEG mixed to form the final gel (Ald-AO-Cat). Ald-AO-Cat has favorable mechanical properties, degradation kinetics, and minimal swelling, as well as superior tissue retention compared to an initial Ald-AO gel formulation. We show that the material is cytocompatible, resists cell adhesion, and led to a reduction in the severity of adhesions in an in vivo rat model. We further show feasibility in a pilot porcine study. The Ald-AO-Cat hydrogel barrier may therefore serve as a promising solution for preventing post-surgical cardiac adhesions.

A simple mouse model of pericardial adhesions

Background

Postoperative pericardial adhesions are considered a risk factor for redo cardiac surgery. Several large- and medium-size animal models of pericardial adhesions have been reported, but small animal models for investigating the development of anti-adhesion materials and molecular mechanisms of this condition are lacking. In this study, we aimed to establish a simple mouse model of pericardial adhesions to address this gap.

Methods

We administered blood, minocycline, picibanil, and talc into the murine pericardial cavity via one-shot injection. Micro-computed tomography analyses of contrast agent-injected mice were carried out for methodological evaluation. We investigated various dosages and treatment durations for molecules identified to be inducers of pericardial adhesion. The adhesive grade was quantified by scoring the strength and volume of adhesion tissues at sacrificed time points. Histological staining with hematoxylin and eosin and Masson’s trichrome, and immunostaining for F4/80 or αSMA was performed to investigate the structural features of pericardial adhesions, and pathological features of the pericardial adhesion tissue were compared with human clinical specimens.

Results

Administration of talc resulted in the most extensive pericardial adhesions. Micro-computed tomography imaging data confirmed that accurate injection into the pericardial cavity was achieved. We found the optimal condition for the formation of strong pericardial adhesions to be injection of 2.5 mg/g talc for 2 weeks. Furthermore, histological analysis showed that talc administration led to an invasion of myofibroblasts and macrophages in the pericardial cavity and epicardium, consistent with pathological findings in patients with left ventricular assistive devices.

Conclusions

We successfully established a simple mouse model of talc-induced pericardial adhesions, which mimics human pathology and could contribute to solving the clinical issues related to pericardial adhesions.

An Absorbable Hydrogel Spray Reduces Postoperative Mediastinal Adhesions After Congenital Heart Surgery

BACKGROUND

Adhesions encountered during reoperative cardiac surgery can prolong operative time and increase operative risk. The purpose of this clinical study was to investigate the antiadhesion property of a synthetic bioabsorbable polymer spray after cardiac reoperations in infants.

METHODS

A prospective randomized double-blinded study was designed. Forty infants requiring staged cardiac operations were randomly allocated to a study group (n = 20) or a control group (n = 20). The appropriate volume of the polymer was sprayed onto the mediastinal surfaces before chest closure after the first surgical procedure in the study group. At reoperation, adhesions were evaluated by a blinded investigator following a 5-grade scoring system. Five predetermined anatomic areas were scored. Incision to extracorporeal circulation time was also analyzed.

RESULTS

In all, 40 subjects were enrolled into the study. Four babies died before the second operation. Three others were missed for reevaluation. The control group (n = 16) had longer incision to extracorporeal circulation time (38 ± 10 minutes) than the study group (n = 17; 23 ± 6 minutes; p < 0.001). The control subjects had significantly more severe adhesions than the study group at all five mediastinal areas: (1) retrosternal (p < 0.001); (2) base of the heart (large vessels [p < 0.05]); (3) right side (p < 0.01); (4) left side (p < 0.02); and (5) diaphragmatic side of the mediastinum (p < 0.001).

CONCLUSIONS

The use of synthetic bioabsorbable polymer sealant spray at the end of primary pediatric cardiac surgery reduces the intensity of mediastinal adhesions and the reentry time in infants undergoing repeat median sternotomy.

Limiting Pericardial Adhesions after Coronary Artery Bypass: Experimental Study

Retrosternal pericardial adhesion formation constitutes a major hazard during re-do coronary artery surgery. To determine whether an onlay parietal pleural flap over the internal thoracic artery bed would reduce pericardial adhesions after coronary artery grafting, 16 sheep underwent a median sternotomy and both internal thoracic arteries were harvested. On the randomly selected study side, a dissected pleural flap was used to cover the internal thoracic artery bed, the opposite side was left uncovered as a control. Half of the sheep were sacrificed at a median of 102 days (range, 93–109 days), the remainder at a median of 176 days (range, 165–183 days). Two independent observers blinded to the initial operation scored the degree of postoperative adhesions. There was a significant decrease in adhesion formation on the study side covered by the mobilized pleural flap, compared to the control side. There were no increases in pulmonary morbidity or sternotomy wound problems from raising the lateral pleural flap. This simple technique appears to be an effective method of preventing adhesion formation following coronary artery bypass grafting utilizing the internal thoracic artery.

Prevention of Esophageal Strictures After Endoscopic Submucosal Dissection: A Promising Therapy Using Carboxymethyl Cellulose Sheets

BACKGROUND

Esophageal stricture is one of the serious adverse events following endoscopic submucosal dissection (ESD). However, optimum preventive techniques are still lacking.

AIMS

Our primary objective was to evaluate the incidence of post-ESD esophageal stricture with the application of carboxymethyl cellulose (CMC) sheets. Secondary objectives were to determine the number of sessions of endoscopic balloon dilatation (EBD) required to resolve post-ESD strictures and the incidence rate of peri-operative adverse events.

METHODS

This was a pilot, single-center, prospective study. Seven patients who had high risks of developing post-ESD esophageal stricture were enrolled into our study. CMC sheets were applied to the mucosal defects immediately after the completion of ESD. Patients were monitored and reviewed after ESD to detect any adverse events.

RESULTS

The incidence rate of post-operative stricture was 57 % (4/7 patients). Among patients who required EBD, the number of sessions performed was 2.8 ± 2.2. No serious post-operative adverse events were reported.

CONCLUSION

The use of CMC sheets appears to be a safe and effective prophylactic treatment for esophageal stricture following extensive ESD.

Binding of Anticell Adhesive Oxime-Crosslinked PEG Hydrogels to Cardiac Tissues

Postsurgical cardiac adhesions increase the number of surgeries as well as patient mortality and morbidity. A fast gelling oxime-crosslinked PEG hydrogel with tunable gelation time, degradation, and mechanical properties is presented. This material is cytocompatible and prevents cellular adhesion. Material retention on different cardiac tissues is demonstrated ex vivo over time and that functional group ratio alters material retention on different cardiac tissues.

Influence of Steroid Therapy on the Incidence of Pericarditis and Atrial Fibrillation After Percutaneous Epicardial Mapping and Ablation for Ventricular Tachycardia

Background—

This study evaluates the influence of 3 therapeutic approaches on the incidence of pericarditis and atrial fibrillation (AF) after percutaneous epicardial mapping and ablation for ventricular tachycardia.

Methods and Results—

Eighty-five consecutive procedures (2006–2011) were retrospectively reviewed. After the first 17 procedures (20.0%), no steroids were administered. For the subsequent 30 procedures (35.3%), systemic steroids were administered intravenously or orally, whereas the last 38 procedures (44.7%) were followed by intrapericardial steroid injection. Compared with no steroids, the incidence of pericarditic chest pain was significantly reduced by intrapericardial steroids (58.8% versus 21.1%; P =0.006) but not by intravenous or oral steroids (58.8% versus 43.4%; P =0.31). There was no significant difference in the incidence of pericarditic ECG with steroids (36.8%, 30.0%, and 41.2% for intrapericardial, intravenous or oral, and none, respectively). There was a nonsignificant reduced incidence of chest pain with ECG changes with steroids (13.2%, 10.0%, and 29.4% for intrapericardial, intravenous or oral, and none, respectively). Radiofrequency applications (65.9% of procedures) did not affect the incidence of pericarditic ECG changes, pericarditic chest pain, or pericarditis (all P >0.05). In 7 (8.3%) patients with no prior history of AF, AF was documented a median 36 hours after procedure. Patients with pericarditic ECG tended to be at greater risk of AF (16.7 versus 3.6%; P =0.091).

Conclusions—

There is a high incidence of pericarditic chest pain and ECG changes after epicardial ventricular tachycardia mapping and ablation. Pericarditic chest pain is significantly decreased by intrapericardial steroids. Procedure-related AF is relatively frequent and tends to occur more commonly with pericarditic ECG changes.

Comparative studies of thermogels in preventing post-operative adhesions and corresponding mechanisms

Thermogelling PLGA–PEG–PLGA, PCGA–PEG–PCGA, and PCL–PEG–PCL triblock copolymers and their efficacies of prevention of post-surgical peritoneal adhesions in rabbits were investigated and compared.

To perform operative procedures in an optimized local atmosphere: can it reduce post-operative adhesion formation?

BACKGROUND

Adhesion formation is a major problem following abdominal surgery as it creates a considerable economic burden in addition to an increased risk for complications. In the present study, an effort was made to reduce post-operative adhesion formation by creating an artificial atmosphere within and around the abdominal cavity during an open surgical procedure.

METHODS

82 Wistar male rats (Clr:WI) (200 gr, 7 weeks) were randomized into two groups. The abdominal cavity of the control group was exposed to the normal atmosphere of the operating-theatre during surgery (21% O₂, 21 °C, 40-47% relative humidity (RH)), while the abdominal cavity of the study group was exposed to an artificial atmosphere during surgery (3-6% O₂, >75% CO₂, 95-100% RH, 37 °C). Adhesion induction consisted of a laparotomy along linea-alba, four lesions in the anterior abdominal-wall, blood from the tail vein dripped inside the abdominal cavity and exposure to the atmosphere around the wound by use of self-retaining retractors. In addition, a liquid-sample for quantitative bacteriologic cultivation and bacterial load (CFU/ml) calculation was taken just before closure. After 3 weeks the abdominal cavity was scored for the extent, tenacity and severity of adhesions before the rats were euthanized. The two-sample-Wilcoxon-rank-sum test was used in the analysis.

RESULTS

Highly significant differences in postoperative total adhesion score, extent-, severity- and tenacity-score were found (P < 0.01). No differences were found between the two groups regarding mean bacterial load (P > 0.05).

CONCLUSIONS

The rats exposed to the warmed and humidified artificial atmosphere consisting of more than 75% carbon dioxide and 3-4% oxygen during surgery had more severe and more post-operative adhesions compared to the rats that were exposed to the ambient air during surgery.

Effect of anti-adhesion barrier solution containing ciprofloxacin-hydrocortisone on abraded mucosa with otitis media

OBJECTIVE

No study to date has assessed the anti-adhesive effect of new middle ear (ME) packing agents in. This study compared the anti-inflammatory and anti-adhesive effect of antibiotic-steroid containing packing agents in abraded mucosa of the ME inflammation.

MATERIALS AND METHODS

Transbullar injection of a saline suspension of Pseudomonas aeruginosa lipopolysaccharide (LPS) induced otitis media. ME mucosa of guinea pigs was abraded using a pick 30 min after LPS inoculation. The animals were divided into four groups of 10 guinea pigs each. In group A, ME cavity was preserved without any packing. In group B, ME cavity was packed with soluble hyaluronic acid-carboxymethyl cellulose (HA-CMC). In group C, the ME cavity was packed with soluble HA-CMC. In group D, the ME cavity was packed with antibiotic-steroid containing soluble HA-CMC. Otoendoscopic examination, auditory brainstem responses (ABRs), and radiographic examination using computerized tomography (CT) were performed at 2 weeks post-surgery. Histopathological evaluation for ME mucosa was performed by light microscopy (LM) and scanning electron microscopy (SEM).

RESULTS

Otoendoscopic findings and CT findings revealed that group D showed the best recovery of aeration in the ME compared to other groups. Recovery of ABRs threshold was significantly attenuated in group D. In LM and SEM findings, group D showed normalized mucosal thickening compared to other groups.

CONCLUSION

ME packing by antibiotic-steroid containing soluble HA-CMC may be useful in the abraded mucosa of the ME inflammation.

Prevention of pleural adhesions by bioactive polypeptides - a pilot study

OBJECTIVE

Postoperative pleural adhesions lead to major problems in repeated thoracic surgery. To date, no antiadhesive product has been proven clinically effective. Previous studies of differently charged polypeptides, poly-L-lysine (PL) and poly-L-glutamate (PG) have shown promising results reducing postoperative abdominal adhesions in experimental settings. This pilot study examined the possible pleural adhesion prevention by using the PL+PG concept after pleural surgery and its possible effect on key parameters; plasmin activator inhibitor-1 (PAI-1) and tissue growth factor beta 1 (TGFb) in the fibrinolytic process.

METHODS

A total of 22 male rats were used in the study, one control group (n=10) and one experimental group (n=12). All animals underwent primary pleural surgery, the controls receiving saline in the pleural cavity and the experimental group the PL+PG solution administered by spray. The animals were evaluated on day 7. Macroscopic appearance of adhesions was evaluated by a scoring system. Histology slides of the adhesions and pleural biopsies for evaluation of PAI-1 and TGFb1 were taken on day 7.

RESULTS

A significant reduction of adhesions in the PL+PG group (p<0.05) was noted at day 7 both regarding the length and severity of adhesions. There were no significant differences in the concentration of PAI-1 and TGFb1 when comparing the two groups.

CONCLUSIONS

PL+PG may be used to prevent pleural adhesions. The process of fibrinolysis, and fibrosis was though not affected after PLPG administration.

Biodegradable and thermoreversible PCLA-PEG-PCLA hydrogel as a barrier for prevention of post-operative adhesion

Biodegradable polymers can serve as barriers to prevent the post-operative intestinal adhesion. Herein, we synthesized a biodegradable triblock copolymer poly(ɛ-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(ɛ-caprolactone-co-lactide) (PCLA-PEG-PCLA). The concentrated polymeric aqueous solution was injectable, and a hydrogel could be rapidly formed due to percolation of a self-assembled micelle network at the body temperature without requirement of any chemical reactions. This physical hydrogel retained its integrity in vivo for a bit more than 6 weeks and was eventually degraded due to hydrolysis. The synthesized polymer exhibited little cytotoxicity and hemolysis; the acute inflammatory response after implanting the hydrogel was acceptable, and the degradation products were less acidic than those of other polyester-containing materials. A rabbit model of sidewall defect-bowel abrasion was employed, and a significant reduction of post-operative peritoneal adhesion has been found in the group of in situ formed PCLA-PEG-PCLA hydrogels.

Bioresorbable adhesion barrier for reducing the severity of postoperative cardiac adhesions: Focus on REPEL-CV(®)

Treatment of a number of congenital heart defects often necessitates staged surgical intervention. In addition, substantial improvements in postoperative cardiac care and more liberal use of biological valve substitutes have resulted in many adult patients surviving to become potential candidates for reoperations to repair or replace valves or to undergo additional revascularization procedures. In all these scenarios, surgeons are confronted with cardiac adhesions, leading to an increased surgical risk. Thus, bioresorbable adhesion barriers had become of increasing interest because they are easy to use, and safe and effective. This review focuses on the mechanisms by which REPEL-CV^® prevents adhesive processes, as well as the development, design, and materials used, and also summarizes efficacy studies, clinical data, safety, and current role in therapy.

CO2 insufflation influences the temperature of the open surgical wound

In open surgery, heat is lost due to radiation and evaporation through the wound. Hypothermia causes tissue hypoxia and impairs various cellular immune functions that increases the risk for postoperative wound infections and delayed wound healing. The patient's body is usually well protected with heating arrangements, but the open wound is left unprotected and until now no practical method has been available to protect it thermically. We therefore investigated if insufflation of an open surgical wound with carbon dioxide would affect wound temperature. In 10 patients undergoing cardiac surgery, the sternotomy wound was insufflated with dry, room temperature carbon dioxide via a gas diffuser for 2 minutes. A heat-sensitive camera measured the wound temperature before, during, and after insufflation. Exposure to carbon dioxide increased the median temperature of the whole wound by 0.5 degrees C (p=0.01). The temperature of the area distant to the diffuser increased by 1.2 degrees C (p<0.01) whereas in the area close to the diffuser it decreased by 1.8 degrees C (p<0.01). In conclusion, short-term insufflation of dry room temperature carbon dioxide in an open wound increases the surface temperature significantly. Although a small increase, it may reduce the incidence of postoperative wound infections in the future.

Effect of adhesion barrier (interceed TC7) on two-stage orchidopexy operation

OBJECTIVE

In two-stage orchidopexy, adhesions formed after the first stage usually cause difficulty during the second operation and may even lead to injury to the testis itself or to the spermatic cord. We investigated whether the use of adhesion-preventing barriers in the abdominal or pelvic region during surgery could lessen adhesions formed during two-stage orchidopexy and thus ease dissection.

MATERIAL AND METHODS

The study subjects comprised 21 male, albino, 30-day-old Wistar rats that were divided into three equal groups. In Group 1, the right testes were enveloped in adhesion barriers after dissection and sutured to the inguinal canal. In Group 2, the right testes were sutured to the inguinal canal without the barriers. In Group 3 (sham-operated group), all testes were dissected but no suturing was performed. Rats were sacrificed after 21 days and the ipsilateral testes were harvested.

RESULTS

Dissection of barrier-enveloped testes was relatively easy; however, no significant (p < 0.535) difference was seen in adhesion scores between Groups 1 and 2. Total tissue collagen was estimated by means of the hydroxyproline content. Tissue hydroxyproline levels were 16.04 +/- 8.58, 13.20 +/- 6.34 and 14.71 +/- 5.51 microg/mg wet tissue in Groups 1-3, respectively and these differences were not significant. The histopathologic evaluation revealed significant differences only in the thickness of the tunica albuginea in Groups 1 and 2 (110.0 +/- 30.0 vs 77.1 +/- 21.3 microm, respectively; p < 0.038).

CONCLUSION

The adhesion scores and the biochemical and histopathological examinations showed that an adhesion barrier is not beneficial in two-stage orchidopexy.

New quantitative variables to measure postoperative pericardial adhesions: useful tools in experimental research

PURPOSE: To improve the measurement system, during a research for the prevention of adhesions, we explored the feasibility of introducing three continuous numeric variables to quantify the intensity of pericardial adhesions. METHODS: To validate these three new numeric variables - time spent to dissect the adhesions (Δt), the amount of sharp dissection (ShpD) and the adhesion's collagen area (ACA) - as useful tools in measuring the severity of pericardial adhesions, data from a randomized study on adhesion prevention enrolling twenty-four swine, were analysed. A statistical Spearman's test and regressions models were applied to verify the correlation and the relationship between the results of a standard severity score (SS) and Δt, between SS and ShpD used in adhesiolysis and, also, between SS and ACA. RESULTS: There was a statistically significant correlation between SS and Δt, between SS and ShpD, as well as between SS and ACA, all measured by the Spearman's test (r=0.897, r=0.932, r=0.66; p<0.01, respectively). Through a non-linear regression, an exponential relation of SS with ShpD (R²=0.915) and SS with Δt (R²= 0.917) was found. CONCLUSION: The time spent to dissect the adhesions (Δt) and the amount of sharp dissection (ShpD) are new powerful measurement tools in evaluating outcomes of the methods used to prevent pericardial adhesions.

Experimental efficacy of pericardial instillation of anti-inflammatory agents during percutaneous epicardial catheter ablation to prevent postprocedure pericarditis

INTRODUCTION

Pericarditis is a potential complication of catheter-based percutaneous epicardial mapping and ablation. This study evaluates the efficacy and safety of intrapericardial instillation of anti-inflammatory agents after pericardial mapping and ablation in a porcine model of postprocedural pericarditis.

METHODS AND RESULTS

Twenty-five healthy swine underwent epicardial mapping and ablation after transthoracic subxyphoid puncture. After 60 minutes of continuous catheter manipulation in the pericardial space, radiofrequency energy was delivered in a linear fashion to the epicardial surfaces of both atria. The animals were randomly divided to receive the anti-inflammatory agents, Hyaluronic Acid and Triamcinolone, or control. Fourteen days after ablation, the hearts were excised and the degree of pericardial reaction/adhesions scored. The severity was uniformly graded 4 (intense) in all control animals and was characterized by intense adhesion between the parietal and the visceral pericardium obscuring tissue planes and epicardial anatomy. Hyaluronic Acid provided a mild benefit (score 3.0 +/- 0.9), but 2 mg/kg of Triamcinolone significantly attenuated the inflammatory effect (all animals uniformly scored 1.0).

CONCLUSION

In a porcine model of ablation-related pericarditis, intrapericardial instillation of 2 mg/kg of intermediate-acting corticosteroids effectively prevents post-procedure inflammatory adhesion formation.

Prevention of Postoperative Pericardial Adhesions With a Novel Regenerative Collagen Sheet

BACKGROUND

Postoperative pericardial adhesions make a repeat sternotomy time-consuming and dangerous. The purpose of this study was to evaluate the efficacy of a new collagen pericardial substitute for preventing postoperative pericardial adhesions.

METHODS

Our absorbable substitute consists of three layers: a middle layer of aterocollagen between two layers of sodium hyaluronic acid and aterocollagen. In experiment 1 in this study, the patch, made of 9,000 filaments of aterocollagen fibers, (group 1; n = 5) was compared with a patch made of 6,000 filaments (group 2; n = 7), an expanded polytetrafluoroethylene sheet (group 3; n = 6), and a control group (group 4; n = 4). Subsequently, in experiment 2, the patch was examined at 4 weeks (n = 5), 12 weeks (n = 5), and 24 weeks (n = 4) after the operation by light microscopy and scanning electron microscopy.

RESULTS

The area of adhesion in group 1 was significantly less as compared with that in the other three groups, and the coronary vessels were clearly identifiable; on the other hand, all the animals in the control group showed moderate to severe adhesions, and the coronary vessels were completely obscured. In experiment 2, formation of a membranous tissue resembling the native pericardial membrane was observed in all animals, and the thickness of this membrane showed a marked increase by 24 weeks after the operation. Light microscopy and scanning electron microscopy also showed the formation of a mesothelium-like lining.

CONCLUSIONS

The new absorbable and regenerative collagen patch seemed to be biocompatible, and its use was associated with minimal adhesion formation and preserved coronary anatomy.

Can Wound Desiccation Be Averted During Cardiac Surgery? An Experimental Study

During cardiac surgery the wound is exposed to desiccation, especially as a result of operating room ventilation and the insufflation of dry carbon dioxide (CO(2)) for de-airing. We compared the gas humidity and desiccation rates in an in vitro model of a cardiothoracic wound during these conditions and during insufflation of humidified CO(2). To assess the influence of flow velocity, CO(2) was insufflated at 10 L/min via two devices, a standard open-ended tube and a low-velocity gas diffuser. The treatment arms were compared with a control without insufflation. When insufflated via the open-ended tube the humidity in the model was almost equal to the control, both with dry and humidified CO(2). However, the total desiccation rate was more rapid than the control (P < 0.001), especially in the area exposed to the gas jet where the desiccation rate was three times more rapid (P < 0.001). With the gas diffuser, dry CO(2) caused almost zero humidity and a desiccation rate that was almost equal to the control. Humidified CO(2) increased humidity in comparison with the control (P < 0.001) and decreased the desiccation rate by >90% (P < 0.001). Humidified CO(2) may be used to avert desiccation of the cardiothoracic wound. The humidified gas is effective only when delivered via a low-velocity outlet device.

Next-Generation HydroGel Films as Tissue Sealants and Adhesion Barriers

BACKGROUND

The development of conveniently sprayed, tissue-adherent, inert hydrogel films has made possible the creation of novel products that can serve a dual function, as a surgical sealant to achieve immediate hemostasis, and as a barrier to prevent adhesion formation over time.

METHODS

A sprayable, in situ formed absorbable hydrogel film was evaluated as a tissue sealant in a heparinized canine carotid artery graft model. PTFE grafts with leaking end-to-side anastomoses were treated with the synthetic sealant, and hemostasis was evaluated upon restoration of blood flow. Also, the hydrogel films were evaluated as an adhesion barrier in a rabbit pericardial abrasion model.

RESULTS

The sprayable, in situ forming hydrogel film was shown to immediately seal carotid-PTFE anastomoses in six of six applications. Hydrogel application in a rabbit pericardial abrasion model resulted in a statistically significant reduction in the number and tenacity of adhesions.

CONCLUSIONS

This novel in situ formed sprayable hydrogel film has demonstrated a dual function as an effective tissue sealant and as an adhesion barrier in cardiovascular preclinical models. These next generation synthetic biomaterials are currently undergoing clinical investigations.

Use of a high-molecular-weight carboxymethylcellulose in a tissue protective solution for prevention of postoperative abdominal adhesions in ponies

OBJECTIVE

To evaluate efficacy and safety of IP administration of high-molecular-weight carboxymethylcellulose (HMW CMC) for the prevention of postoperative intra-abdominal adhesions in ponies.

ANIMALS

10 ponies.

PROCEDURE

A 1% solution of HMW CMC was instilled intra-abdominally prior to surgery in 5 ponies, whereas 5 control ponies did not receive HMW CMC. Postoperative adhesions were induced by use of a bowel-abrasion method comprising laparotomy, typhlotomy, and abrasion of jejunal serosa at multiple sites with placement of 3 sutures at each site. Day of surgery was day 0. After surgery, ponies were monitored, and hematologic, serum biochemical, and peritoneal fluid analyses were performed on days 1, 2, 3, 5, 7, and 10. On day 10, ponies were euthanatized. Intra-abdominal adhesions were recorded, and tissue samples were collected for histologic examination.

RESULTS

A significantly greater number of adhesions, number of multiple adhesions, and mean incidence of adhesions were identified in control ponies, compared with CMC-treated ponies. Mean peritoneal fluid WBC count on day 7 and serum fibrinogen concentrations on days 5 and 7 were significantly higher in control ponies, compared with CMC-treated ponies. Results of serum biochemical analyses did not differ significantly between the 2 groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Intra-abdominal use of 1% HMW CMC during surgery was effective for preventing postoperative adhesions in ponies. Use of HMW CMC did not have detrimental effects on wound healing, intra-abdominal defenses, or patient health. A 1% solution of HMW CMC may be used routinely during abdominal surgery of horses for prevention of postoperative adhesions.

Effects of angiotensin type-I receptor blockade on pericardial fibrosis

BACKGROUND

Reoperative cardiac surgical procedures are associated with a significantly greater complication rate than that of the initial procedure. Enhanced collagen synthesis can occur due to increased production of angiotensin II (Ang-II) and subsequent activation of Ang AT(1) receptor. Accordingly, the goal of the current study is to test the hypothesis that increased Ang AT(1) receptor activity following pericardiotomy contributes to pericardial thickening and fibrosis.

MATERIALS AND METHODS

Adult pigs were randomly assigned to three protocols: (1) pericardiotomy with 28-day recovery period (n = 5); (2) pericardiotomy with Ang AT(1) receptor blockade instituted throughout the 28-day recovery period using 60 mg/day valsartan (n = 5); and (3) sham controls (n = 6). Pericardium samples were collected and analyzed by biochemical and histomorphometrical methods. Pericardial fibrosis occurred postpericardiotomy as indicated by increased hydroxyproline content from normal value of 50 +/- 3 microg/mg to 75 +/- 4 microg/mg (P < 0. 05).

RESULTS

Pericardial thickness was increased postpericardiotomy to 2.7 +/- 0.4 mm compared to normal values of 0.4 +/- 0.05 mm (P < 0.05). Ang AT(1) receptor blockade reduced pericardial thickness by 50% and the relative degree of fibrosis was comparable to that of the normal group.

CONCLUSIONS

The results from this pericardial fibrosis animal model suggest that Ang AT(1) receptor activation contributes to the development of pericardial thickening and collagen accumulation in the postoperative period. Thus, Ang AT(1) receptor inhibition may provide a novel therapeutic strategy to prevent pericardial fibrosis that follows cardiac surgical procedures.