Efficacy of three adhesion-preventing agents in reducing severe peritoneal trauma induced by bipolar coagulation in a laparoscopic rat model

Comparison of Honey versus Polylactide Anti-Adhesion Barrier on Peritoneal Adhesion and Healing of Colon Anastomosis in Rabbits

BACKGROUND:

Postoperative adhesion is still a consequence of intra-abdominal surgeries, which results in bowel obstruction and abdominopelvic pain. Bowel anastomosis as a common abdominal surgery has the incidence of leakage in up to 30% of patients that increase morbidity and mortality. Due to similar pathways of adhesion formation and wound healing, it is important to find a way to reduce adhesions and anastomosis leakage.

AIM:

This study was designed to compare antiadhesive as well as anastomosis healing improvement effect of honey and polylactide anti-adhesive barrier film.

METHODS:

Forty-five rabbits divided into three groups of honey, adhesion barrier film, and control group in an animal study. Under a similar condition, rabbits underwent resection and anastomosis of cecum under general anaesthesia. In the first group, honey was used at the anastomosis site, in the second one polylactide adhesion barrier film utilised, and the third one was the control group. Adhesion, as well as anastomosis leakage, was assessed after 21 days. Data were analysed using the Statistical Package for Social Scientists (SPSS) for Windows version 25.

RESULTS:

Three groups of 15 rabbits were studied. The results showed that mean peritoneal adhesion score (PAS) was lower in the honey group (1.67) in comparison to the adhesion barrier film group (3.40) and the control group (6.33).

CONCLUSION:

Bio-absorbable polylactide barrier has an anti-adhesion effect but is not suitable for intestinal anastomosis in rabbits. Further studies needed to evaluate these effects on human beings.

Polymer materials for prevention of postoperative adhesion

Postoperative adhesion (POA) is a common complication that often occurs after a variety of surgeries, such as plastic surgery, repair operations of abdominal, pelvic, and tendon, and so forth. Moreover, POA leads to chronic abdominal pain, secondary infertility in women, intestinal obstruction, and other severe complications, which significantly reduce the life quality of patients. In order to prevent the formation of POA, a number of strategies have been developed, among which an emerging method is physical barriers consisting of polymer materials. This review highlights the most commonly used natural and synthetic polymer materials in anti-adhesion physical barriers. The specific features of polymer materials are analyzed and compared, and the possible prospect is also predicted.

STATEMENT OF SIGNIFICANCE

Postoperative adhesion (POA) is a serious complication accompanied with various surgeries. Polymer material-based physical barriers have attracted a large amount of attention in POA prevention. The polymer barriers can effectively avoid the formation of fibrous tissues among normal organs by reducing the interconnection of injured tissues. In this review, specific features of the natural and synthetic polymer materials for application in POA prevention were presented, and the possible prospects were predicted. All in all, our work can provide inspiration for researchers to choose proper polymer materials for preclinical and even clinical anti-adhesion studies.

A Novel Method for Evaluating Postoperative Adhesions in Rats

Purpose/Aim: Postoperative adhesions remain an undesirable and commonly symptomatic side effect of abdominopelvic surgeries. Animal models of postoperative adhesions typically yield heterogeneous adhesions throughout the abdominal cavity and are not easily quantified. Here we present a novel method of postoperative adhesion assessment and report its reliability and measurement error.

MATERIALS AND METHODS

A model of cecal abrasion with partial sidewall attachment was performed on female rats. After 1, 2, 4, or 7 days of recovery, the rats were euthanized and their abdominopelvic cavities were systematically evaluated for postoperative adhesions. The necropsy was recorded through the surgical microscope. Four raters were trained to use a ballot to capture key factors of the adhesions as they viewed the recordings. Their ratings were compared for measurement error and reliability (using Bland-Altman plots and intraclass correlation coefficients, respectively) and for the ability to discriminate differences in experimental groups. A subset of the data was analyzed to determine practical utility.

RESULTS

The rating system was shown to have low measurement error and high inter-rater reliability for all parameters measured. Applied practically, the system was able to discriminate groups in a manner that was expected.

CONCLUSIONS

We have developed and validated a rating system for postoperative adhesions and shown that it can detect group differences. This method can be used to quantify postoperative adhesions in rodent models.

Regulation of synthesis and roles of hyaluronan in peritoneal dialysis

Hyaluronan (HA) is a ubiquitous extracellular matrix glycosaminoglycan composed of repeated disaccharide units of alternating D-glucuronic acid and D-N-acetylglucosamine residues linked via alternating β-1,4 and β-1,3 glycosidic bonds. HA is synthesized in humans by HA synthase (HAS) enzymes 1, 2, and 3, which are encoded by the corresponding HAS genes. Previous in vitro studies have shown characteristic changes in HAS expression and increased HA synthesis in response to wounding and proinflammatory cytokines in human peritoneal mesothelial cells. In addition, in vivo models and human peritoneal biopsy samples have provided evidence of changes in HA metabolism in the fibrosis that at present accompanies peritoneal dialysis treatment. This review discusses these published observations and how they might contribute to improvement in peritoneal dialysis.

Standardised models for inducing experimental peritoneal adhesions in female rats

Animal models for adhesion induction are heterogeneous and often poorly described. We compare and discuss different models to induce peritoneal adhesions in a randomized, experimental in vivo animal study with 72 female Wistar rats. Six different standardized techniques for peritoneal trauma were used: brushing of peritoneal sidewall and uterine horns (group 1), brushing of parietal peritoneum only (group 2), sharp excision of parietal peritoneum closed with interrupted sutures (group 3), ischemic buttons by grasping the parietal peritoneum and ligating the base with Vicryl suture (group 4), bipolar electrocoagulation of the peritoneum (group 5), and traumatisation by electrocoagulation followed by closure of the resulting peritoneal defect using Vicryl sutures (group 6). Upon second look, there were significant differences in the adhesion incidence between the groups (P < 0.01). Analysis of the fraction of adhesions showed that groups 2 (0%) and 5 (4%) were significantly less than the other groups (P < 0.01). Furthermore, group 6 (69%) was significantly higher than group 1 (48%) (P < 0.05) and group 4 (47%) (P < 0.05). There was no difference between group 3 (60%) and group 6 (P = 0.2). From a clinical viewpoint, comparison of different electrocoagulation modes and pharmaceutical adhesion barriers is possible with standardised models.

Comparative stability of the bioresorbable ferric crosslinked hyaluronic acid adhesion prevention solutions

The Intergel® ferric crosslinked hyaluronate (FeHA) adhesion prevention solution (APS) (FDA) is associated with serious post-operative complications (Henley, http://www.lawyersandsettlements.com/features/gynecare-intergel/intergel-timeline.html, 2007; FDA, 2003; Roman et al., Fertil Steril 2005, 83 Suppl 1:1113-1118; Tang et al., Ann Surg 2006;243(4):449-455; Wiseman, Fertil Steril 2006;86(3):771; Wiseman, Fertil Steril 2006;85(4):e7). This prompted us to examine the in situ stability of crosslinked HA materials to hyaluronidase lyase degradation. Variables such as ferric ionic crosslink density, HA concentration, gel geometry, and molecular weight (MW) of HA polymer were studied. Various formulations of the crosslinked "in house" [Isayeva et al., J Biomed Mater Res: Part B - Appl Biomater 2010, 95B (1):9-18] FeHA (0.5%, w/v; 30, 50, 90% crosslinked), the Intergel® FeHA (0.5%, w/v; 90%), and the non-crosslinked HA (0.05-0.5%, w/v) were degraded at a fixed activity of hyaluronidase lyase from Streptomyces hyalurolyticus (Hyase) at 37°C over time according to the method [Payan et al., J Chrom B: Biomed Sci Appl 1991;566(1):9-18]. Under our conditions, the data show that the crosslink density affects degradation the most, followed by HA concentration and then gel geometry. We found that MW has no effect. Our results are one possible explanation of the observations that the Intergel® FeHA APS (0.5%, w/v; 90%) material persisted an order of magnitude longer than expected [t1/2 = 500 hrs vs. t1/2 = 50 hrs (FDA; Johns et al., Fertil Steril 1997;68(1):37-42)]. These data also demonstrate the sensitivity of the in vitro hyaluronidase assay to predict the in situ stability of crosslinked HA medical products as previously reported [Sall et al., Polym Degrad Stabil 2007;92(5):915-919].

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.

Intraperitoneal adhesions--an ongoing challenge between biomedical engineering and the life sciences

Peritoneal adhesions remain a relevant clinical problem despite the currently available prophylactic barrier materials. So far, the physical separation of traumatized serosa areas using barriers represents the most important clinical strategy for adhesion prevention. However, the optimal material has not yet been found. Further optimization or pharmacological functionalization of these barriers could give an innovative input for peritoneal adhesion prevention. Therefore, a more complete understanding of pathogenesis is required. On the basis of the pathophysiology of adhesion formation the main barriers currently in clinical practice as well as new innovations are discussed in the present review. Physiologically, mesothelial cells play a decisive role in providing a frictionless gliding surface on the serosa. Adhesion formation results from a cascade of events and is regulated by a variety of cellular and humoral factors. The main clinically applied strategy for adhesion prevention is based on the use of liquid or solid adhesion barriers to separate physically any denuded tissue. Both animal and human trials have not yet been able to identify the optimal barrier to prevent adhesion formation in a sustainable way. Therefore, further developments are required for effective prevention of postoperative adhesion formation. To reach this goal the combination of structural modification and pharmacological functionalization of barrier materials should be addressed. Achieving this aim requires the interaction between basic research, materials science and clinical expertise.

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.

A membrane slurry reduces postoperative adhesions in rat models of abdominal surgery

BACKGROUND

Sodium hyaluronate and carboxymethylcellulose (HA-CMC) membrane is an effective barrier material for limiting postoperative adhesions, but can be difficult to apply in certain situations due to its physical properties. We tested whether HA-CMC membrane hydrated in saline (slurry) is an effective alternative to HA-CMC membrane for preventing surgical adhesions in rat models of abdominal surgery.

MATERIALS AND METHODS

All studies were performed in rat cecal abrasion or sidewall defect models of adhesion formation. Adhesions were examined 7 d after surgery. In separate studies, the effects of variations in slurry composition, volume, and site of application on anti-adhesive properties were studied and compared with untreated controls. Finally, the effectiveness of HA-CMC membrane slurry for preventing adhesions was compared with that of conventional HA-CMC membrane.

RESULTS

Application of HA-CMC membrane slurry to traumatized tissue resulted in a significant reduction in the incidence of adhesions compared with untreated controls in both rat surgery models. Slurry was equally effective when applied in low and high film-to-volume formulations, but had minimal effect when applied in a small volume or at a location distal to the injury. Comparison of HA-CMC membrane slurry and conventional HA-CMC membrane indicated similar efficacy for reducing postoperative adhesions.

CONCLUSIONS

In rat models of abdominal surgery, HA-CMC membrane slurry reduced postoperative adhesion formation and may be an effective alternative for HA-CMC membrane in situations where its use is limited by its physical properties.

Prevention of postoperative adhesion formation by individual and combined administration of 4 per cent icodextrin and dimetindene maleate

BACKGROUND

To date, no single method has been successful in eliminating peritoneal adhesion formation after major abdominal surgery. This study evaluated the individual and possible synergistic effect of a local intraperitoneal barrier, 4 per cent icodextrin, and an intravenously administered antihistamine drug, dimetindene maleate, in the prevention of adhesion development following surgical trauma.

METHODS

De novo experimental adhesions were induced by standardized trauma of the peritoneum and large bowel in 120 New Zealand White rabbits. The animals were randomized into four groups receiving intraperitoneal saline, intraperitoneal 4 per cent icodextrin (60 ml), intravenous dimetindene maleate (0.1 mg/kg) and 4 per cent icodextrin-dimetindene in combination (n = 30 per group). Ten days later, adhesion scores and incidence were assessed by two independent surgeons. and surface area by computer-aided planimetry.

RESULTS

Treatment with either icodextrin or dimetindene maleate significantly reduced adhesion scores and increased the incidence of adhesion-free animals in an equipotent manner. The effect of combined treatment on severity, incidence and surface area of adhesions was more pronounced than that of each drug administered separately.

CONCLUSION

Combined administration of 4 per cent icodextrin and dimetindene maleate may be used safely and efficaciously to prevent surgically induced adhesions.

The new adhesion prophylaxis membrane A-part--from in vitro testing to first in vivo results

INTRODUCTION

Formation of postoperative intra-abdominal adhesions is a severe problem in surgery. Apart from standard surgical procedures, a variety of different substances is available to prevent adhesions, but no universal method has been developed so far. A membrane consisting of polyvinyl alcohol (PVA) and carboxymethylcellulose (CMC) has been demonstrated to be antiadhesive. Here, the in vitro testing and first in vivo results in a rabbit sidewall model are reported.

MATERIALS AND METHODS

A-part membrane contains a PVA/CMC mixture in a thickness of 40 microm. The composition, dissolution, tensile strength, and elasticity were examined to characterize the membrane in vitro. Experiments in vivo were carried out using a 'rabbit sidewall model' in which a standardized peritoneal trauma was covered with a 5 x 6 cm A-part membrane. Adhesion formation in A-part-treated animals was compared with that in Adept (15 mL/kg body weight) and untreated controls.

RESULTS

An 80/20 PVA/CMC mixture forms a stable, elastic, transparent membrane, which can easily be placed intraoperatively. The dissolution shows a half-life of about 2 weeks [day 15: (45.1 +/- 4.9)% SD], which affords good adhesion protection during the initial critical phase of adhesion formation. In wet conditions, the membrane follows abdominal movements without tearing (tensile strength 5.0 +/- 4.2 N/cm SD; elasticity 29.5%). In a rabbit sidewall model, A-part membrane significantly reduced adhesion development by (83.1 +/- 31.5)% SD compared with the control and the Adept group (p < 0.001).

CONCLUSION

The properties of the A-part membrane suggest that it may be useful as an antiadhesive in surgery. A-part is effective in in vivo testing as determined in a rabbit sidewall model.

Efficacy of barriers and hypoxia-inducible factor inhibitors to prevent CO(2) pneumoperitoneum-enhanced adhesions in a laparoscopic mouse model

STUDY OBJECTIVE

To investigate the effects of hypoxia-inducible factor (HIF) inhibitors, flotation agents, barriers, and a surfactant on pneumoperitoneum-enhanced adhesions in a laparoscopic mouse model.

DESIGN

Prospective randomized trial (Canadian Task Force classification I).

SETTING

Department of Obstetrics and Gynecology, University Hospital Gasthuisberg, Catholic University of Leuven.

SUBJECTS

One hundred fourteen female BALB/c mice.

INTERVENTIONS

Adhesions were induced during laparoscopy in BALB/c female mice. Pneumoperitoneum was maintained for 60 minutes with humidified CO(2). In 3 experiments the effects of HIF inhibitors such as 17-allylamino 17-demethoxygeldanamycin, radicicol, rapamycin, and wortmanin, flotation agents such as Hyskon and carboxymethylcellulose, barriers such as Hyalobarrier gel and SprayGel, and surfactant such as phospholipids were evaluated.

MEASUREMENTS AND MAIN RESULTS

Adhesions were scored after 7 days during laparotomy. Adhesion formation decreased with the administration of wortmannin (p <.01), phospholipids (p <.01), Hyalobarrier Gel (p <.01), and SprayGel (p <.01).

CONCLUSIONS

These experiments confirm the efficacy of barriers and phospholipids to separate or lubricate damaged surfaces. They also confirm the role of mesothelial hypoxia in this model by the efficacy of the HIF inhibitor wortmannin.

Ovarian endometrioma: postoperative adhesions following bipolar coagulation and suture

OBJECTIVE

To compare bipolar coagulation and suturing of the ovary in terms of postoperative ovarian adhesions after laparoscopic ovarian cystectomy for endometriosis.

DESIGN

Prospective, randomized, controlled study.

SETTING

Department of Obstetrics and Gynecology, University of Naples "Federico II."

PATIENT(S)

Thirty-two women with a single endometriotic cyst were randomly divided into two groups of 16 women each (groups A and B).

INTERVENTION(S)

All patients underwent laparoscopic ovarian cystectomy for endometriosis. In group A, hemostasis was performed by closure of the ovary with an intraovarian suture. In group B, complete hemostasis was achieved only with bipolar coagulation on the internal face of the ovary.

MAIN OUTCOME MEASURE(S)

Rate and extension of postsurgical ovarian adhesions at 60-90 days follow-up.

RESULT(S)

At follow-up, a significantly lower rate of postsurgical ovarian adhesions was observed in group A than in group B (30.8% vs. 57.1%). The extension of ovarian adhesions was significantly higher in group B than in group A.

CONCLUSION(S)

The use of sutures on ovaries treated for endometrioma is associated with a lower rate of postoperative ovarian adhesion formation compared with bipolar coagulation.

Effect of reactive oxygen species scavengers, antiinflammatory drugs, and calcium-channel blockers on carbon dioxide pneumoperitoneum-enhanced adhesions in a laparoscopic mouse model

BACKGROUND

Postoperative adhesions are a clinical problem. They can cause female infertility, intestinal obstruction, chronic pelvic pain, and difficulties at the time of reoperation. A variety of approaches described to prevent adhesions have shown variable and inconsistent results. Therefore, this study aimed to evaluate most known substances in a laparoscopic mouse model to obtain quantitative and comprehensive information on adhesion prevention. Specifically, this first study aimed to investigate the effects of reactive oxygen species (ROS) scavengers, antiinflammatory agents, and a calcium-channel blocker on pneumoperitoneum-enhanced adhesions.

METHODS

Adhesions were induced during laparoscopy in BALB/c female mice by creation of a bipolar lesion. Carbon dioxide (CO2) pneumoperitoneum was maintained for 60 min using humidified CO2. Six experiments were conducted to evaluate the effects of ROS scavengers (superoxide dismutase [SOD], catalase, melatonin, and ascorbic acid), antiinflammatory agents (dexamethasone, tenoxicam, ibuprofen, parecoxib, nimesulide, anti-tumor necrosis factor [TNF]-alpha), and a calcium-channel blocker (diltiazem). Adhesions were scored after 7 days during laparotomy.

RESULTS

Adhesions were reduced by SOD (p < 0.01, proc general linear methods (GLM) of experiments 1 and 2), diltiazem (p = 0.05, Wilcoxon), and dexamethasone (p < 0.03), but not by nonsteroidal antiinflammatory drugs (NSAIDs) nor by anti-TNF-alpha. When all the experiments were grouped for analysis, adhesions also decreased with one and three doses of SOD (p < 0.01 and p < 0.01, respectively) and with one and three doses of ascorbic acid (p < 0.02 and p = 0.05, respectively).

CONCLUSIONS

These experiments confirm that SOD, diltiazem, and dexamethasone can decrease adhesion formation. The absence of effect from the other antiinflammatory drugs and anti-TNF-alpha is surprising.

Efficiency of 4% Icodextrin in Preventing Adhesions to Spiral Tacks Used to Fix Intraperitoneal Prostheses

BACKGROUND/AIMS

This study was designed to evaluate the extent of adhesion formation to prostheses fixed with spiral tacks and to establish whether the use of Ringer's lactate or icodextrin could prevent these adhesions.

METHODS

24 New Zealand white rabbits weighing around 3,000 g were implanted with a 7 x 5 cm patch of ePTFE (DualMesh) through a midline laparotomy. The prosthesis was fixed to the intact peritoneum using spiral tacks. Three study groups were established according to whether the animals were: implanted with ePTFE fixed with spiral tacks or implanted with ePTFE fixed with spiral tacks and simultaneously administered Ringer's lactate or 4% icodextrin in the peritoneal cavity. Adhesion formation and prosthetic behavior at the prosthesis/peritoneal interface were evaluated and quantified by sequential laparoscopy performed at 3, 7 and 14 days.

RESULTS

Adhesions generally formed on the tacks and were classified as the fully integrated type. No significant differences were observed in terms of the extent of adhesions or of neoperitoneal thickness between control animals and those receiving Ringer's lactate or icodextrin.

CONCLUSIONS

(a) Prosthesis-fixing tacks induced adhesions; (b) the use of substances such as icodextrin or Ringer's lactate does not seem to diminish adhesion formation, and (c) the use of icodextrin offered no benefits over that of Ringer's lactate solution.