Formation and prevention of postoperative abdominal adhesions

Bladder Injury During Cesarean Delivery

Cesarean section is the most common surgery performed in the United States with over 30% of deliveries occurring via this route. This number is likely to increase given decreasing rates of vaginal birth after cesarean section (VBAC) and primary cesarean delivery on maternal request, which carries the inherent risk for intraoperative complications. Urologic injury is the most common injury at the time of either obstetric or gynecologic surgery, with the bladder being the most frequent organ damaged. Risk factors for bladder injury during cesarean section include previous cesarean delivery, adhesions, emergent cesarean delivery, and cesarean section performed at the time of the second stage of labor. Fortunately, most bladder injuries are recognized at the time of surgery, which is important, as quick recognition and repair are associated with a significant reduction in patient mortality. Although cesarean delivery is a cornerstone of obstetrics, there is a paucity of data in the literature either supporting or refuting specific techniques that are performed today. There is evidence to support double-layer closure of the hysterotomy, the routine use of adhesive barriers, and performing a Pfannenstiel skin incision versus a vertical midline subumbilical incision to decrease the risk for bladder injury during cesarean section. There is also no evidence that supports the creation of a bladder flap, although routinely performed during cesarean section, as a method to reduce the risk of bladder injury. Finally, more research is needed to determine if indwelling catheterization, exteriorization of the uterus, and methods to extend hysterotomy incision lead to bladder injury.

The aromatase inhibitor letrozole reduces adhesion formation after intraperitoneal surgery in a rat uterine horn model

OBJECTIVE

To investigate, in an experimental animal study, the effects of letrozole and tamoxifen in the reduction of adhesion formation following abdominopelvic surgery.

STUDY DESIGN

Thirty female Wistar albino rats were included and divided into three groups. One group received 500 μg/d tamoxifen and a second group received 1 mg/kg/d letrozole through an enteric tube. A third group did not receive any drugs and served as the control group. On the fifth day, a laparotomy was performed and the right uterine horn was injured by monopolar cautery. The left uterine horn was incised with a scalpel and sutured. The preventive therapy protocols were continued for 7 days after surgery. On the 14th day after first surgery the animals were sacrificed, and the intraperitoneal macroscopic adhesion formation and microscopic adhesion features were evaluated. The Kruskal-Wallis test was used to compare the scores of the macroscopic adhesion scores and histologic features among the three groups, followed by a post hoc Mann-Whitney test. The total histological score was analyzed with a one-way ANOVA, followed by post hoc Bonferroni correction tests. p values ≤0.05 were considered statistically significant. The level of significance was set at p≤0.016 for the post hoc tests.

RESULTS

The letrozole and tamoxifen groups had significantly lower adhesion scores for the right uterine horn than the control group (p=0.005 and p=0.013, respectively). For the left horn, however, only the letrozole group had a lower macroscopic adhesion score than the controls (p=0.011). The total histological score was significantly lower in the letrozole group than in the control group (p=0.014), but no differences were found between the tamoxifen group and the control group (p=0.954). Inflammation, fibroblastic activity, collagen formation and vascular proliferation were significantly lower in the letrozole group compared with the control group (p<0.05). The foreign body reactions were similar among the three groups (p>0.05). Tamoxifen administration did not result in any significant effects on the histological scores (p>0.05).

CONCLUSION

Letrozole resulted in a significant decrease in postoperative macroscopic adhesion formation and the total histological scores, but tamoxifen did not demonstrate a similar effect on the histological scores.

Novel powdered anti-adhesion material: preventing postoperative intra-abdominal adhesions in a rat model

BACKGROUND

Although laparoscopic surgery has decreased postoperative adhesions, complications induced by adhesions are still of great concern. The aim of this study was to investigate the anti-adhesive effects of a novel powdered anti-adhesion material that can be applied during laparoscopic surgery in comparison with other anti-adhesion materials.

METHODS

Our novel powdered anti-adhesion material is composed of aldehyde dextran and ε-poly(L-lysine). In 40 male rats, a 2.5×2.0-cm abdominal wall resection and cecum abrasion were performed. The rats were randomized into four groups based on the anti-adhesion treatments: normal saline; Seprafilm(®); Interceed(®); and novel powdered anti-adhesion material. The animals were euthanized on days 7 and 28 to evaluate the adhesion severity, area of adhesion formation, gross appearance, and pathological changes.

RESULTS

The adhesion severities on both days 7 and 28 were significantly lower for all anti-adhesion material groups compared with the normal saline group (p<0.05). Pathologically, all groups showed inflammatory cell infiltration on day 7 and complete regeneration of the peritoneum on day 28.

CONCLUSIONS

Our novel powdered anti-adhesion material was found to be effective for reducing postoperative intra-abdominal adhesions and showed equivalent efficacy to commercial anti-adhesion materials.

Adhesion-preventing properties of 4% icodextrin and canola oil: a comparative experimental study

OBJECTIVE

Postsurgical abdominal adhesions are common, serious postoperative complications. The present study compared the usefulness of 4% icodextrin and canola oil in preventing postoperative peritoneal adhesions.

METHODS

Twenty-four Wistar albino rats were divided into three groups. Following a laparotomy, a serosal abrasion was made by brushing the cecum, and 3 mL of 0.9% NaCl, 4% icodextrin, or 3 mL of canola oil were intraperitoneally administered for the control, icodextrin, and canola oil groups, respectively. The abdomen was then closed. All of the rats were sacrificed at day 10. Macroscopic, histopathological, and biochemical evaluations were performed. The results were statistically analyzed using Kruskal-Wallis and ANOVA tests.

RESULTS

Macroscopic analyses revealed that both canola oil and 4% icodextrin reduced adhesion formation, but the difference was not statistically significant (p = 0.17). The histopathological examinations revealed no significant differences in terms of giant cell, lymphocyte/plasmocyte, neutrophil, ICAM1, or PECAM1 scores. However, both canola oil and 4% icodextrin significantly reduced fibrosis (p = 0.025). In the canola oil group, the histiocytic reactions were significantly increased (p = 0.001), and the hydroxyproline levels were significantly lower than those in the other groups (p = 0.034).

CONCLUSIONS

In the present study, canola oil was determined to be superior to 4% icodextrin in lowering hydroxyproline levels and increasing histiocytic reactions. Considering these results, we believe that canola oil is a promising agent for preventing adhesion formation.

Halofuginone infused keratin hydrogel attenuates adhesions in a rodent cecal abrasion model

BACKGROUND

Postoperative adhesion formation continues to be a significant surgical complication, and methods for preventing abdominopelvic adhesions remain limited. Halofuginone (HF) is a type-1 collagen synthesis inhibitor and may enhance the effects of a physical barrier in preventing adhesion formation. We evaluated the effectiveness of a HF infused keratin hydrogel on preventing adhesions in a rat cecal abrasion model.

MATERIAL AND METHODS

Laparotomy and standardized cecal abrasion was performed on 58 retired-breeder Sprague Dawley female rats to induce intra-abdominal adhesions. Rats were randomized to: no treatment; Interceed absorbable adhesion barrier; keratin hydrogel alone; or keratin hydrogel infused with 22 μg/mL of HF. Necropsies were performed at postop d-14 to assess the extent and tenacity of adhesions and grade histologic inflammation and fibrosis using a standard scoring system. Serum, liver, kidneys, and lungs were harvested to evaluate tissue HF concentrations. Protein and drug elution curves were generated to assess the release of HF from the hydrogel.

RESULTS

Treatment with Keratin-HF hydrogel resulted in significantly fewer abdominal adhesions than any other treatment, and significantly less dense adhesions compared with Interceed or keratin hydrogel alone. Subset histologic analysis did not reveal qualitative differences. HF was undetectable in serum and kidneys, and detected at negligible concentrations in liver and lungs. Keratin-HF hydrogel drug release in phosphate-buffered solution (PBS) was sustained over 7 d and correlated with keratin protein degradation.

CONCLUSIONS

Keratin-HF hydrogel is a novel therapeutic agent that may provide a better method for preventing the development of postoperative adhesions using a combined physical barrier and pharmacologic approached.

Mesothelial morphology and organisation after peritoneal treatment with solid and liquid adhesion barriers--a scanning electron microscopical study

Separation of traumatized tissue represents the only promising strategy in postoperative adhesion prevention, a relevant clinical problem after surgical intervention. In the present study scanning electron microscopy (SEM) and subsequent morphometry were used to analyse the tissue response to five commercial adhesion barriers. Standardised peritoneal lesions in Wistar rats were covered with solid and viscous barrier materials and semiquantitatively analysed 14 days postoperatively. Striking morphological differences in lesion surface organisation between the barrier groups became apparent with colonisation of the barrier by mesothelial cells to different degrees. Furthermore, the mesothelial cells showed either a normal or activated phenotype depending on the underlying biomaterial. These experiments demonstrate that the examination by SEM gives useful insights into the performance of barrier materials and the cellular processes of adhesion prevention, since mesothelial cells play an active role in the pathogenesis of adhesion formation.

Comparison of 4 % icodextrin and omega 3 Fatty acids in prevention of peritoneal adhesions

Postoperative peritoneal adhesions are major concerns in abdominal surgery. In this experimental study, the effects of 4 % icodextrin and omega-3 fatty acids (ω-3 FA) on prevention of postoperative peritoneal adhesions were evaluated. Twenty-four Wistar albino rats were divided into three groups. After laparotomy, serosal abrasion was carried out by cecal brushing. Intraperitoneally 3 cm(3) 0.9 % NaCl, 3 cm(3) 4 % icodextrin, and 200 mg/kg ω-3 FAs for each group were applied, and then the abdomen was closed. All subjects sacrificed 10 days postoperatively. Macroscopic and histopathological cellular reactions as a function of giant cell, lymphocyte/plasmocyte, neutrophil, histiocyte, intracellular adhesion molecule-1 (ICAM-1), and platelet endothelial cell adhesion molecule-1 (PECAM-1) were assessed and hydroxyproline levels were measured in all three groups and compared using Kruskal-Wallis and ANOVA tests when appropriate. Macroscopically, both ω-3 FAs and 4 % icodextrin reduced adhesion formation but the difference was not statistically significant (P = 0.253). Histopathological examination revealed that there was no statistical significance in terms of giant cell, lymphocyte/plasmocyte, neutrophil, ICAM-1, and PECAM-1 scores; however, both ω-3 FAs and 4 % icodextrin were found to be prone to reduce fibrosis (P = 0.047), whereas in the ω-3 FA group, histiocytic reaction was significantly increased (P = 0.001), and hydroxyproline levels were significantly lower than other groups (P = 0.044). In this study, ω-3 FAs were found to be superior to 4 % icodextrin with the lower hydroxyproline level and greater histiocytic reaction. Considering these results, ω-3 FAs can be a promising agent in the prevention of adhesion formation.

Intraperitoneal adhesions after open or laparoscopic abdominal procedure: an experimental study in the rat

BACKGROUND

Adhesion formation is common after abdominal surgery. The incidence and severity of adhesion formation following open or laparoscopic surgery remain controversial. The role of CO(2) pneumoperitoneum is also widely discussed. This study aimed to compare adhesion formation following peritoneal injury by electrocoagulation performed through open or laparoscopic procedures in a rat model.

MATERIALS AND METHODS

Sixty male rats were randomized to undergo a 1.5-cm peritoneal injury with unipolar cautery under general anesthesia: open surgery (Group A, n=20), laparoscopic surgery with CO(2) pneumoperitoneum (Group B, n=20), and laparoscopic surgery with air pneumoperitoneum (Group C, n=20). Duration of the procedures was fixed at 90 minutes in all groups, and pneumoperitoneum pressure was kept at 10 mm Hg. Ten days later, the animals underwent a secondary laparotomy to score peritoneal adhesions using qualitative and quantitative parameters.

RESULTS

Forty-five rats developed at least one adhesion: 95% in Group A, 83% in Group B, and 55% in Group C (P<.01; Group C versus Group A, P<.01). According to number, thickness, tenacity, vascularization, extent, type, and grading according to the Zühkle classification, no significant difference was observed between Groups A and B. The distribution of adhesions after open surgery was significantly different than after laparoscopic surgery (P<.001). It is interesting that Group C rats developed significantly fewer adhesions at the traumatized site, and their adhesions had less severe qualitative scores compared with those after open surgery (P<.01).

CONCLUSIONS

In this animal model, CO(2) laparoscopic surgery did not decrease the formation of postoperative adhesion, compared with open surgery. The difference with the animals operated on with air pneumoperitoneum emphasizes the role of CO(2) in peritoneal injury leading to adhesion formation.

Current strategies and future perspectives for intraperitoneal adhesion prevention

INTRODUCTION

The formation of peritoneal adhesions still is a relevant clinical problem after abdominal surgery. Until today, the most important clinical strategies for adhesion prevention are accurate surgical technique and the physical separation of traumatized serosal areas. Despite a variety of barriers which are available in clinical use, the optimal material has not yet been found.

DISCUSSION

Mesothelial cells play a crucial physiological role in friction less gliding of the serosa and the maintenance of anantiadhesive surface. The formation of postoperative adhesions results from a cascade of events and is regulated by various cellular and humoral factors. Therefore, optimization or functionalization of barrier materials by developments interacting with this cascade on a structural or pharmacological level could give an innovative input for future strategies in peritoneal adhesion prevention. For this purpose, the proper understanding of the formal pathogenesis of adhesion formation is essential. Based on the physiology of the serosa and the pathophysiology of adhesion formation, the available barriers in current clinical practice as well as new innovations are discussed in the present review.

A sprayable hyaluronate/carboxymethylcellulose adhesion barrier exhibits regional adhesion reduction efficacy and does not impair intestinal healing

BACKGROUND

While bioresorbable solid barriers such as Seprafilm® prevent adhesions, their efficacy is limited to sites of application. The aim of this study was to assess the effectiveness of the sprayable adhesion barrier Sepraspray® in preventing adhesions to sites of direct application and to remote sites.

METHODS

Intraabdominal adhesions were induced in 30 rats by creating three ischemic buttons on each side of a midline incision. To assess efficacy, Sepraspray (5 mg/button) or Seprafilm (1 cm(2)/button) was applied over three buttons on one side of the peritoneum. Operated control animals received no treatment. On day 7, adhesions were scored as percent of buttons with adhesions. To assess safety, 81 rats underwent a colonic transection repaired with an end-to-end anastomosis. Both barriers were applied circumferentially to anastomoses. Controls received no product. The integrity of healing anastomosed colonic wounds was assessed by burst pressure and tensile strength at days 3, 5, and 7 postoperatively.

RESULTS

The direct application of both Sepraspray and Seprafilm significantly (p < 0.001) reduced adhesion formation compared to controls. While Seprafilm had no remote effect on adhesion formation, Sepraspray significantly (p < 0.001) reduced adhesion formation to contralateral ischemic buttons. Neither barrier affected anastomotic integrity at any time point.

CONCLUSIONS

Sepraspray has widespread efficacy throughout the peritoneum in reducing adhesions without compromising intestinal healing. Furthermore, this sprayable alternative offers the potential for easier intraabdominal application.

Adhesion prevention in patients with multiple cesarean deliveries

Adhesion formation is a well-known complication of abdominal surgery. Although one third of all deliveries in the United States are by cesarean delivery (CD), little is known about adhesions in the obstetric setting. Various surgical techniques for reducing adhesion formation following CD have been investigated. The relative benefits of peritoneal closure and single-layer uterine closure are areas of continued research and debate. Adhesion prevention products are also becoming more commonplace in gynecologic surgery. Two membrane/adhesion barriers have been approved in the United States. A barrier consisting of oxidized regenerated cellulose (Interceed absorbable adhesion barrier) has been shown to reduce adhesions during microsurgery. Its use may be limited following CD because complete hemostasis is crucial to its efficacy. Seprafilm adhesion barrier, composed of hyaluronic acid and carboxymethylcellulose, is approved for use in abdominal or pelvic laparotomy. Preliminary data suggest that it may be effective for reducing adhesions following CD. This article discusses what is currently known about adhesion prevention in the obstetric population and highlights the paucity of level I evidence available to clinicians in this setting.

Adhesions and perioperative complications of repeat cesarean delivery

The unprecedented high rate of cesarean delivery and the declining rate of vaginal birth after cesarean delivery make necessary awareness of the potential complications that are associated with repeat cesarean delivery. This article reviews the epidemiologic features of cesarean delivery and the perioperative risks that are associated with repeat cesarean delivery. These risks include increased adhesions, infections and wound complications, bleeding, bowel injury and obstruction, hysterectomy, operative time, hospital stay, and delays in delivery.

Pathophysiology and prevention of postoperative peritoneal adhesions

Peritoneal adhesions represent an important clinical challenge in gastrointestinal surgery. Peritoneal adhesions are a consequence of peritoneal irritation by infection or surgical trauma, and may be considered as the pathological part of healing following any peritoneal injury, particularly due to abdominal surgery. The balance between fibrin deposition and degradation is critical in determining normal peritoneal healing or adhesion formation. Postoperative peritoneal adhesions are a major cause of morbidity resulting in multiple complications, many of which may manifest several years after the initial surgical procedure. In addition to acute small bowel obstruction, peritoneal adhesions may cause pelvic or abdominal pain, and infertility. In this paper, the authors reviewed the epidemiology, pathogenesis and various prevention strategies of adhesion formation, using Medline and PubMed search. Several preventive agents against postoperative peritoneal adhesions have been investigated. Their role aims in activating fibrinolysis, hampering coagulation, diminishing the inflammatory response, inhibiting collagen synthesis or creating a barrier between adjacent wound surfaces. Their results are encouraging but most of them are contradictory and achieved mostly in animal model. Until additional findings from future clinical researches, only a meticulous surgery can be recommended to reduce unnecessary morbidity and mortality rates from these untoward effects of surgery. In the current state of knowledge, pre-clinical or clinical studies are still necessary to evaluate the effectiveness of the several proposed prevention strategies of postoperative peritoneal adhesions.

Intra-abdominal adhesions: cellular mechanisms and strategies for prevention

Postoperative intra-abdominal adhesions represent a serious clinical problem. In this review, we have focused on recent progress in the cellular and humoral mechanisms underpinning adhesion formation, and have reviewed strategies that interfere with these pathways as a means to prevent their occurrence. Current and previous English-language literature on the pathogenesis of adhesion formation was identified. As the burden of surgical disease in the world population increases, and the frequency of reoperation increases, prevention of adhesion formation has become a pressing goal in surgical research.

Fibrin-targeted block copolymers for the prevention of postsurgical adhesions

Despite advances in surgical methods, postsurgical adhesions (PSA) remain a significant clinical challenge affecting millions of patients each year. These permanent fibrous connections between tissues result from the bridging of wounded internal surfaces by an extended fibrin gel matrix (FGM). Adhesion formation is a result of a systems level convergence of wound healing pathways, complicating the design of materials that could inhibit their occurrence. In this study, a systematic approach that identifies key material properties required for functional performance optimization was used to design a new fibrin-targeted PSA prevention material. A series of multifunctional polymers with varied molecular architectures was synthesized to investigate the effect of changing polymer structural parameters on the ability to disrupt the formation of an extended FGM. Initial studies in a murine adhesion model demonstrated a statistically significant reduction in the degree of PSA formation, demonstrating the potential value of this systematic approach.

Administration of a novel penicillamine-bound membrane: a preventive and therapeutic treatment for abdominal adhesions

BACKGROUND

Adhesions formation is a significant postsurgical complication. At present, there is no effective method for preventing adhesions formation 1, although barrier products such as Dextran (Dex) 2 and sodium hyaluronate (SH) 3 have proved the most clinically successful 456, This study is designed to investigate the preventive and therapeutic potential of a novel penicillamine-bound membrane for abdominal adhesions formation.

METHODS

150 rats were involved in the present study. All animals were randomly divided into 6 groups (1 vehicle group and 5 test groups respectively treated with dextran, sodium hyaluronate, penicillamine, penicillamine-bound membrane or non-penicillamine-bound membrane). The occurrence, grade and score of abdominal adhesions were compared between the different groups. The breaking strength of incision was compared between the vehicle group and the penicillamine, membrane with/without penicillamine - treated groups. Expression of collagen type I was compared between the vehicle and penicillamine-treated group. The occurrence of adhesions was compared between the Dextran (Dex), sodium hyaluronate (SH), penicillamine-treated group and membrane with or without penicillamine- treated groups.

RESULTS

Penicillamine and penicillamine-bound membrane had significant preventive effects on abdominal adhesions formation, better than dextran, sodium hyaluronate and non-penicillamine-bound membrane. However, neither of them influenced incision healing, although they insignificantly decreased the breaking strength of the incision. Penicillamine-bound membrane, which can be loaded locally and more efficaciously, shows greater advantages than penicillamine.

CONCLUSIONS

Penicillamine-bound membrane can be applied as an effective therapeutic intervention for abdominal adhesions with inconsequential side effects.

A hydrogel for adhesion prevention: characterization and efficacy study in a rabbit uterus model

OBJECTIVE

Postoperative peritoneal adhesions following gynaecological surgery remain a clinically relevant problem. One approach to prevent adhesion formation is to apply physical barriers such as hydrogels.

STUDY DESIGN

A physically crosslinked polyvinyl alcohol and carboxymethylcellulose (PVA/CMC) hydrogel (A-Part) was characterized in vitro. Three different traumatization methods were evaluated in a rabbit uterine study. To determine its anti-adhesion efficacy, the hydrogel was first tested in an in vivo pilot study and then in a larger trial to compare it with icodextrin 4% solution (Adept) and controls.

RESULTS

Rheological measurements showed an increased elasticity of the hydrogel after freezing. In vivo experiments revealed a clear reduction in incidence, extent and severity of adhesions compared to the icodextrin 4% solution and the untreated control group.

CONCLUSIONS

These results warrant further investigation of the PVA/CMC A-Part hydrogel in clinical trials focused on gynaecological procedures.

2-hydroxyethyl methacrylate composite - polypropylene mesh for preventing peritoneal adhesions in female dogs

PURPOSE

To evaluate whether the lining facing the visceral side of polypropylene mesh made with 2-hydroxyethyl methacrylate (p(HEMA)) hydrogel could avoid peritoneal adhesion in female dogs.

METHODS

Eight animals (group PP) had a polypropylene mesh implanted to correct a defect in the rectal abdominal muscle, whereas in the other group (group PH) the polypropylene mesh was coated with p(HEMA) composite on the surface facing the peritoneal area.

RESULTS

Adhesions were observed on the mesh in 62.5% of the PP group. In the PH group adhesions were present only on the suture lines.

CONCLUSION

p(HEMA) hydrogel was well tolerated and effective in avoiding visceral and omental adhesions on the surface of the polypropylene mesh.

A pilot study of laparoscopic adhesion prophylaxis after myomectomy with a copolymer designed for endoscopic application

STUDY OBJECTIVE

To assess the laparoscopic handling and safety of D,L-polylactide-epsilon-caprolactone-trimethylene carbonate (PCT) copolymer after myomectomy and compare it with icodextrin. In contrast to previously developed solid barriers, the material has rationally designed properties that are advantageous for convenient laparoscopic application.

DESIGN

A randomized, single-blinded clinical study (Canadian Task Force Classification I).

SETTING

Single-center study in a German University Hospital.

PATIENTS

Thirty patients who underwent laparoscopic myomectomy were enrolled.

INTERVENTIONS

After laparoscopic myomectomy and subsequent reconstruction of the uterus with interrupted sutures, adhesion prophylaxis with either site-specific PCT copolymer or icodextrin occurred as per randomization.

MEASUREMENTS AND MAIN RESULTS

Except in 1 case, complete coverage of the uterine wound was achieved with PCT copolymer, and the mean time taken for application was 6.7 minutes. Mean application time for icodextrin was 1.1 minute. After introduction into the abdomen, PCT copolymer changed into a flexible state that adapted very well to the operative anatomy. The patients were followed up according to the study protocol for 3 months. There were no unforeseen adverse events, possible adhesion-related complications, or nonspecific complications in either study arm. There was no significant difference in pelvic pain scores between PCT copolymer and icodextrin groups 3 months after surgery.

CONCLUSION

In this pilot study, there were no adverse events, and the rationally designed material properties are favorable for laparoscopic application. No differences in postoperative pelvic pain were ascertained between PCT copolymer and icodextrin. Therefore a human phase II trial including second-look laparoscopy should be conducted to further evaluate this new solid adhesion barrier PCT copolymer.

Osmotic nephrosis due to the use of anti-adhesive membrane intraperitoneally

BACKGROUND

A common strategy for the prevention of intra-abdominal adhesions post-operatively has been the application of adhesion barriers into the peritoneal cavity. Side effects of these barriers are infection, abscesses and inadequate wound healing. There is no information about such a side effect of these materials on renal function. The aim of this study was to evaluate the effect of two different, commercially available polysaccharide-based anti-adhesive materials on renal function.

METHODS

In 24 adult Wistar rats, an abdominal midline incision was performed, and an anti-adhesion membrane was placed in the peritoneal cavity so as to cover its whole surface. Four rats were used as the control group. In 12 rats, a membrane of macromolecular polysaccharides, weighing 40 mg/cm2, was placed intra-abdominally and in 8 rats, a hyaluronic acid-hydroacidmethylcellulose membrane weighing 0.4 mg/cm2 was placed. At 24 or 70 h, the rats were sacrificed, and we evaluated changes in serum creatinine, urea, uric acid, K and Na, and histologic examination of the kidney was performed.

RESULTS

The use of the thicker macromolecular membrane was associated with a rise in serum creatinine and urea levels, vacuolization of all the tubular epithelial cells and mild interstitial infiltration. Rats in which the hyaluronic acid-hydroacidmethylcellulose membrane was used did not show any creatinine elevation, and they presented milder histologic lesions.

CONCLUSION

Polysaccharide and cellulose anti-adhesive membrane cause renal damage with tubular cell vacuolization. The severity of kidney damage is relative to the quantity of the membrane material used.

Prevention of intra-peritoneal adhesions in gynaecological surgery: theory and evidence

Post-operative adhesions are a significant complication of all abdominal surgical procedures. The major strategies for adhesion prevention in gynaecological surgery are focused on the optimization of surgical technique and use of anti-adhesive agents, which fall into two main categories: pharmacological agents and barriers. Surgical technique that minimizes peritoneal trauma can reduce, but cannot prevent post-operative adhesion formation. Various local and systemic drugs that can alter the local inflammatory response, inhibit the coagulation cascade and promote fibrinolysis have been evaluated. Limited data support the administration of post-operative corticosteroids in addition to systemic intra-operative corticosteroids for the prevention of adhesions after gynaecological surgery. None of the remaining pharmacological agents have been found effective for the reduction of post-operative adhesions. Barriers are currently considered the most useful adjuncts, which may reduce adhesion formation. They act by separating the traumatized peritoneal surfaces during the healing period. The separation can be achieved by solid barriers or fluids. There is limited evidence from randomized clinical trials that support the beneficial effect of most of these barrier agents in the prevention of intra-peritoneal adhesions after gynaecological surgery. However, the evidence is not adequate for definite conclusions to be drawn and further research in this field is warranted.

Block copolymers for the rational design of self-forming postsurgical adhesion barriers

Post-surgical adhesions, abnormal fibrous linkages between adjacent tissue surfaces, represent one of the most common and significant complications facing surgical recovery today. Physical barriers and gels have been the most successful at limiting their formation, yet are not effective in cases where the pro-adhesive site is either unknown or difficult to reach (e.g. during laparoscopic surgery). In this work, poly(methacrylic acid-co-t-butylmethacrylate)-b-poly(ethylene glycol (M(N) = 1000) methacrylate) diblock and statistical copolymers were synthesized as a platform for designing self-forming adhesion barriers, which can attach to exposed pro-adhesive sites through binding with the positively charged extracellular matrix, basement membrane proteins and deposited fibrin. An experimental model based upon a quartz crystal microbalance with dissipation was developed to test the diblock copolymers ability (i) to adsorb to an amine-terminated self-assembled monolayer, and (ii) to inhibit subsequent protein adsorption. These results were also confirmed using an in vitro cell attachment model. As the mole fraction of methacrylic acid content increased, polymer adsorption increased. All synthesized diblock copolymers investigated provided high resistance to protein adsorption, with blockade ranging from 55% to 81%. Except for the uncharged control polymers, the ability of these materials to resist cellular attachment showed similar trends, with the suppression of attachment approaching 75%. Energy dissipation analysis and variable-angle spectroscopic ellipsometry revealed two competing adsorption mechanisms depending on the molecular properties of the polymer.

Functional polymers as therapeutic agents: concept to market place

Biologically active synthetic polymers have received considerable scientific interest and attention in recent years for their potential as promising novel therapeutic agents to treat human diseases. Although a significant amount of research has been carried out involving polymer-linked drugs as targeted and sustained release drug delivery systems and prodrugs, examples on bioactive polymers that exhibit intrinsic therapeutic properties are relatively less. Several appealing characteristics of synthetic polymers including high molecular weight, molecular architecture, and controlled polydispersity can all be utilized to discover a new generation of therapies. For example, high molecular weight bioactive polymers can be restricted to gastrointestinal tract, where they can selectively recognize, bind, and remove target disease causing substances from the body. The appealing features of GI tract restriction and stability in biological environment render these polymeric drugs to be devoid of systemic toxicity that are generally associated with small molecule systemic drugs. The present article highlights recent developments in the rational design and synthesis of appropriate functional polymers that have resulted in a number of promising polymer based therapies and biomaterials, including some marketed products.

Characterizing omental adhesions by culturing cells isolated from a novel in vivo adhesion model

Although it has been established that postoperative adhesions in the peritoneal cavity are the consequence of injury to the peritoneum, there is much controversy over the nature of the cells giving rise to this neotissue. Here, we establish a novel adhesiogenic model in the rabbit to analyze the phenotype and proliferation in vitro of cells comprising adhesion tissue seven days postsurgery. Adhesion-free omentum tissue was used as control. Cells derived from adhesions and from the control omentum were subcultured and characterized through immunofluorescence and Western blotting procedures to determine markers of cell differentiation and pluripotential, and viability and proliferation assays. Our findings indicate the existence of a mesenchymal population in the omentum revealed by markers of pluripotent cells with high angiogenic capacity. This population seems to be responsible for the adhesions formed in response to mesothelial damage. Depending on the local environment, mesenchymal cells are capable of in vivo differentiation towards at least two different cell phenotypes rendering two types of adhesions with clearly differentiated characteristics. One type of adhesion shows a highly vascularized adipose morphology containing cells differentiating into a vascular lineage. The other adhesions are fibrous with large amounts of collagen and comprised mainly of myofibroblasts conferring less compliance to this tissue.

A direct comparison of seprafilm, adept, intercoat, and spraygel for adhesion prophylaxis

BACKGROUND

Commercially available agents for adhesion prophylaxis are legion but there is a lack of direct comparisons between them. Here we compare four of the most commonly used adhesion barriers against a control group in a clinically relevant rat model.

MATERIAL AND METHODS

Standardized lesions were created in Wistar rats using electrocautery and suturing. Subsequently, the experimental lesions were treated with Seprafilm (n = 30), Adept (n = 30), Intercoat (n = 30), Spraygel (n = 30), or no barrier (n = 30). The resulting adhesions were examined 14 d postoperatively.

RESULTS

The mean area covered by adhesion was 77% in the control group, 46% in animals treated with Seprafilm, 54% in animals treated with Adept, 55% in animals treated with Intercoat, and 68% in animals treated with Spraygel. The adhesion-free incidence was 20% (n = 6) of lesions treated with Seprafilm, 20% (n = 6) of lesions treated with Intercoat, 3% of lesions treated with Spraygel (n = 1), and 0% of lesions treated with Adept or the control group.

CONCLUSIONS

There were statistically significant differences between the barriers with regards to the area covered by adhesions and the adhesion-free incidence. In spite of this, a significant adhesion burden remains with all of the tested barriers.

The effects of intraperitoneal sildenafil administration on healing of left colonic anastomoses and intra-abdominal adhesion formation in the presence of intra-abdominal infection

PURPOSE

The objective of this pilot study was to establish an animal model for intra-abdominal infection and to examine the effect of sildenafil on anastomotic healing of the left colon and intra-abdominal adhesion formation.

METHODS

Fourteen Winstar rats underwent colonic transsection and primary anastomosis after performing intra-abdominal infection. Rats were divided into two groups: Group 1 (n = 7): intra-abdominal infection, resection, and anastomoses; Group 2 (n = 7): intra-abdominal infection, resection, anastomoses, and sildenafil. Anastomotic bursting pressures, hydroxyproline levels, histopathologic grading, and abdominal adhesions were accessed on the postoperative Day 7.

RESULTS

Anastomotic healing was found to be improved in terms of a bursting pressure (P = 0.02). Histopathological examination revealed an increase in angiogenesis (P = 0.007). Moreover, intra-abdominal adhesions were significantly less in rats given sildenafil (P = 0.03).

CONCLUSION

Sildenafil may improve anastomotic healing of the left colon and diminishes peritoneal adhesion formation in the presense of abdominal infection.

Sterile Intra-Abdominal Fluid Collection Associated with Seprafilm Use

Postoperative abdominal adhesions are a significant cause of morbidity and expenditure of healthcare resources. As a result, numerous substances have been studied in an effort to reduce the incidence of adhesive disease. Seprafilm, a hyaluronate-based bioresorbable membrane, has been the subject of considerable research and has been found to be both safe and effective in reducing postoperative adhesions. We report three cases of the development of sterile abdominal fluid collection after the use of Seprafilm in colorectal surgery.

An FDA approved neurokinin-1 receptor antagonist is effective in reducing intraabdominal adhesions when administered intraperitoneally, but not orally

INTRODUCTION

Postoperative adhesions pose a continued healthcare problem. We previously demonstrated that intraperitoneal (i.p.) administration of a neurokinin-1 receptor antagonist (NK-1RA) at surgery reduces intraabdominal adhesions in rats. The NK-1RA aprepitant (Emend, Merck) is clinically approved for preventing postoperative nausea and vomiting; however, its effects on adhesion formation are unknown. Thus, we determined the effects of i.p. and oral administration of aprepitant on adhesion formation in a rat model.

METHODS

Adhesions were surgically induced in rats that were randomized to receive either one or five oral preoperative doses or a single intraoperative i.p. dose of aprepitant (50 mg/kg). Adhesions were scored at 7 days. In similar experiments using i.p. dosing, animals were sacrificed at 24 h and peritoneal fluid, and tissue were collected to assess fibrinolytic activity and tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) mRNA levels, respectively.

RESULTS

I.p. aprepitant reduced adhesion formation by 33% (p < 0.05) compared with controls while oral aprepitant had no effect. Compared to controls i.p. aprepitant reduced tPA activity by 55% (p < 0.05), increased PAI-1 mRNA levels by 140% (p < 0.05), and had no affect on tPA mRNA levels.

CONCLUSION

These data suggest that aprepitant maybe a useful pharmacologic agent for reducing adhesion formation clinically.