Practical limitations of bioresorbable membranes in the prevention of intra-abdominal adhesions

What Should I Use? Impact of Adhesion Barriers on Postoperative Abdominal Complications: A Systematic Review

BACKGROUND

Adhesions are a feared complication of abdominal surgery. There have been many new adhesion barriers developed and tested; however, there is no recent systematic review analyzing all the published literature. To address this, we aimed to analyze the different types of adhesion barriers, and determine their effects on postoperative outcomes in patients.

METHODS

A total of 14,038 articles utilizing adhesion barriers in abdominal surgery were retrieved from the PubMed, EMBASE, and Scopus databases. Inclusion criteria were: patients undergoing abdominal surgery, patients receiving an adhesion barrier, and reported postoperative outcomes. Two reviewers independently screened titles/abstracts and full-text articles using Covidence. The ROBINS-I tool was used to assess the quality of the included studies. Study protocol: Prospero CRD42023458230.

RESULTS

A total of 20 studies, with no overall high risk of bias, with 171,792 patients were included. Most studies showed an equivocal benefit for adhesion barriers, with no singular adhesion barrier type that had definitive superior outcomes compared to the others. Bioresorbable barriers emerged as the most extensively researched adhesion barrier type, exhibiting promising results in colorectal surgery. Starch-based adhesion barriers also exhibited a reduction in overall postoperative bowel obstructions and may be beneficial for stoma sites and port closures. On the other hand, many studies raised concerns regarding complications, including risk of abscess formation, fistula development, peritonitis, and anastomotic leakage.

CONCLUSIONS

Adhesion barriers should be considered on a case-by-case basis, however, they should not be utilized prophylactically in all abdominal surgeries due to their risk of complications.

Barrier materials for prevention of surgical adhesions: systematic review

BACKGROUND

Postoperative surgical adhesions constitute a major health burden internationally. A wide range of materials have been evaluated, but despite constructive efforts and the obvious necessity, there remains no specific barrier widely utilized to prevent postoperative adhesion formation. The aim of this study was to highlight and characterize materials used for prevention of postoperative surgical adhesions in both animal and human studies.

METHODS

A systematic review was performed of all original research articles presenting data related to the prevention of postoperative adhesions using a barrier agent. All available observational studies and randomized trials using animal models or human participants were included, with no restrictions related to type of surgery. PubMed and Embase databases were searched using key terms from inception to August 2019. Standardized data collection forms were used to extract details for each study and assess desirable characteristics of each barrier and success in animal and/or human studies.

RESULTS

A total of 185 articles were identified for inclusion in the review, with a total of 67 unique adhesion barrier agents (37 natural and 30 synthetic materials). Desirable barrier characteristics of an ideal barrier were identified on review of the literature. Ten barriers achieved the primary outcome of reducing the incidence of postoperative adhesions in animal studies followed with positive outputs in human participants. A further 48 materials had successful results from animal studies, but with no human study performed to date.

DISCUSSION

Multiple barriers showed promise in animal studies, with several progressing to success, and fulfilment of desirable qualities, in human trials. No barrier is currently utilized commonly worldwide, but potential barriers have been identified to reduce the burden of postoperative adhesions and associated sequelae.

Beta-D-Glucan Levels With Use of an Anti-adhesion Barrier Film in Pediatric Living Donor Liver Transplantation

INTRODUCTION

Serum beta-D-glucan (BDG) levels may increase with anti-adhesion barrier film (ABF) use during pediatric living donor liver transplantation (LDLT). It may affect detection of fungal infections after LDLT. We evaluate BDG levels after pediatric LDLT.

METHODS

Pediatric patients who received an ABF during LDLT were included. Patients who may have had fungal infections prior to LDLT were excluded. One sheet of ABF was placed in the peritoneum during abdominal closure. Serum BDG levels before transplantation and on postoperative days (PODs) 1, 4, 7, 14, 21, and 28 and peritoneal fluid BDG levels on PODs 1 and 7 were measured.

RESULTS

Sixteen patients received an ABF during LDLT. Median age at transplant was 1.9 years (range, 6-11 years). Median body weight was 12.6 kg (range, 6.8-39 kg). Indications for LDLT were biliary atresia (n = 10) and other (n = 5). Prior to transplantation, the mean serum BDG level was 3.8 pg/mL. Mean Serum BDG levels were 18.1, 38.3, 5.3, 3.8, 3.3, and 3.3 pg/mL on PODs 1, 4, 7, 14, 21, and 28, respectively. Mean peritoneal fluid BDG levels were 485.9 and 240.4 pg/mL on PODs 1 and 7, respectively. No clinical fungal infections were observed.

CONCLUSIONS

BDG levels were high in serum and peritoneal fluid after pediatric LDLT. Serum BDG levels normalized after POD 7. Careful interpretation of BDG levels until POD 7 is needed when an ABF has been used.

Effect of Hydrogen-Rich Saline on Postoperative Intra-Abdominal Adhesion Bands Formation in Mice

Background

Postsurgical peritoneal adhesions (PPAs) are pathologic fibrous bands within the peritoneal cavity. The aim of this study was to investigate the protective effect of hydrogen-rich saline (HRS) on PPAs formation in mice.

Material/Methods

Adhesions were induced in mice using the cecum rubbing model. The mice were allocated into 4 groups: control sham group without cecum rubbing; PPA group with saline applied intraperitoneally (i.p.) daily after cecum rubbing; PPA+HRS (5) group with 5 ml/kg of HRS applied i.p. daily after cecum rubbing; and PPA+HRS (10) group with 10 ml/kg of HRS applied i.p. daily after cecum rubbing. On the 1^st, 3^rd, and 7^th days after the operation, mice were killed and pathological adhesion bands were quantified to detect the effect of HRS on PPAs formation.

Results

HRS did not affect PPAs formation on the 1^st day, but did make a significant reduction on the 3^rd and 7^th days. A significant increase of t-PA and decrease of TGF-β1 and PAI-1 in the peritoneal fluids were observed in the HRS-treated groups. The levels of MDA and MPO in the HRS-treated groups were significantly lower than those in the PPA group. TNF-α and IL-6 levels in HRS-treated groups significantly decreased compared with those in the PPA group on postoperative day 3 and 7. Moreover, HRS decreased the mRNA levels of pro-inflammatory cytokines and TGF-β1 expression in the postsurgical adhesion bands.

Conclusions

These results showed that HRS had therapeutic potential for preventing PPAs formation, possibly through balancing the expression of TGF-β1, t-PA, and PAI-1, and inhibiting oxidative stress and inflammation.

A pectin-honey hydrogel prevents postoperative intraperitoneal adhesions in a rat model

Background

Adhesions are a common postoperative surgical complication. Liquid honey has been used intraperitoneally to reduce the incidence of these adhesions. However, solid barriers are considered more effective than liquids in decreasing postoperative intra-abdominal adhesion formation; therefore, a new pectin-honey hydrogel (PHH) was produced and its effectiveness was evaluated in a rat cecal abrasion model.

Standardized cecal/peritoneal abrasion was performed through laparotomy in 48 adult Sprague-Dawley rats to induce peritoneal adhesion formation. Rats were randomly assigned to a control (C) and treatment (T) group. In group T, PHHs were placed between the injured peritoneum and cecum. Animals were euthanized on day 15 after surgery. Adhesions were evaluated macroscopically and adhesion scores were recorded and compared between the two groups. Inflammation, fibrosis, and neovascularization were histologically graded and compared between the groups.

Results

In group C, 17 of 24 (70.8%) animals developed adhesions between the cecum and peritoneum, while in group T only 5 of 24 (20.8%) did (p = 0.0012). In group C, one rat had an adhesion score of 3, sixteen had scores of 2, and seven rats had scores of 0. In group T, four rats had adhesion scores of 2, one rat had an adhesion score of 1 and nineteen have score 0 (p = 0.0003). Significantly lower grades of inflammation, fibrosis, and neovascularization were seen in group T (p = 0.006, p = 0.001, p = 0.002, respectively).

Conclusion

PHH is a novel absorbable barrier that is effective in preventing intra-abdominal adhesions in a cecal abrasion model in rats.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-0965-z) contains supplementary material, which is available to authorized users.

Peritoneal adhesion prevention with a biodegradable and injectable N,O-carboxymethyl chitosan-aldehyde hyaluronic acid hydrogel in a rat repeated-injury model

Postoperative peritoneal adhesion is one of the serious issues because it induces severe clinical disorders. In this study, we prepared biodegradable and injectable hydrogel composed of N,O-carboxymethyl chitosan (NOCC) and aldehyde hyaluronic acid (AHA), and assessed its anti-adhesion effect in a rigorous and severe recurrent adhesion model which is closer to clinical conditions. The flexible hydrogel, which gelated in 66 seconds at 37 °C, was cross-linked by the schiff base derived from the amino groups of NOCC and aldehyde groups in AHA. In vitro cytotoxicity test showed the hydrogel was non-toxic. In vitro and in vivo degradation examinations demonstrated the biodegradable and biocompatibility properties of the hydrogel. The hydrogel discs could prevent the invasion of fibroblasts, whereas fibroblasts encapsulated in the porous 3-dimensional hydrogels could grow and proliferate well. Furthermore, the hydrogel was applied to evaluate the anti-adhesion efficacy in a more rigorous recurrent adhesion model. Compared with normal saline group and commercial hyaluronic acid (HA) hydrogel, the NOCC-AHA hydrogel exhibited significant reduction of peritoneal adhesion. Compared to control group, the blood and abdominal lavage level of tPA was increased in NOCC-AHA hydrogel group. These findings suggested that NOCC-AHA hydrogel had a great potential to serve as an anti-adhesion candidate.

Evaluation of the xenobiotic reaction against hyaluronate-based bioresorbable membrane in the abdominal cavity

Postoperative abdominal adhesions are one of the most common post-laparotomy complications observed. Several types of adhesion preventative agents are available and their effectiveness and adverse impact have been clinically evaluated in previous studies. However, few basic studies have tested whether those agents do not trigger any unwanted xenobiotic reaction, which makes some surgeons hesitant to use them. To clarify this point, we investigated whether the adhesion preventative agent Seprafilm^® (KAKEN PHARMACEUTICAL CO., LTD., Tokyo, Japan), one of the most widely used hyaluronate-based bioresorbable membrane (HBBM), can trigger an inflammatory response in normal abdominal tissue and delay the healing process. The rat underwent laparotomy and a HBBM was placed directly below the incision. Tissue samples at the incision and away from the incision (normal tissue) were harvested and inflammatory response and fibrosis were evaluated using quantitative PCR and histological scoring. We found that HBBM did not induce inflammatory cytokine expression at mRNA level in the peritoneal wall tissue or modify the fibrosis process in the abdominal cavity. These findings confirm the safety of using HBBM for the prevention of adhesion development post-laparotomy.

Ghrelin ameliorates adhesions in a postsurgical mouse model

BACKGROUND

Peritoneal adhesion formation is a well-recognized consequence of abdominal and pelvic surgery, causing infertility, chronic pelvic pain, and intestinal obstruction. We hypothesized that ghrelin, a 28-amino acid peptide predominantly found in the stomach, plays an important role in preventing postoperative surgical adhesions. The purpose of this study was to develop a new surgical peritoneal adhesion model to define the role that ghrelin plays in wound healing and adhesion formation.

MATERIALS AND METHODS

C57BL/6 wild-type mice (n = 40) and growth hormone secretagogue receptor-knockout (GHSR KO) mice (n = 20) underwent a midline laparotomy to establish a peritoneal adhesion model characterized by the combination of two different techniques: ischemic peritoneal buttons and cecal multiple abrasion. All mice received intraperitoneal injections with ghrelin (0.16 mg/kg) or saline twice daily for 20 d after surgery. Peritoneal ischemic buttons were harvested to determine protein expression of collagen (Masson trichrome, picrosirius red stain, and Western blot).

RESULTS

The novel mouse model demonstrated consistent and easily reproducible formation of intra-abdominal adhesions. Ghrelin administration significantly reduced postoperative adhesion formation (P < 0.001) in wild-type mice. The antifibrotic effect of ghrelin in wild-type mice was confirmed by measuring collagen I protein levels via Western blot analysis. The anti-adhesion effect of ghrelin seen in wild-type mice was not detected in GHSR KO mice demonstrating that this effect is mediated by the GHSR-1a receptor.

CONCLUSIONS

Ghrelin administration may improve surgical outcome by reducing peritoneal adhesion formation and fibrotic response in a mouse model.

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.

Cell-based therapy for preventing postoperative adhesion and promoting regeneration after hepatectomy

Postoperative adhesion is a critical clinical issue after almost all abdominal or pelvic surgeries including liver surgery. Postoperative adhesion causes several complications, such as small bowel obstruction and chronic abdominal pain. Furthermore, it makes reoperation much more difficult, leading to increased mortality and morbidity rate. Postoperative adhesion is particularly problematic for repeated hepatectomy, since hepatic malignant neoplasm recurs frequently and repeated hepatectomy is widely used as one of the most curative treatments. Several treatments to reduce postoperative adhesion have been developed, which include laparoscopic surgery, administration of pharmacological agents and use of prophylactic barrier materials. However, none of them are optimal. We have proposed a novel treatment using a cell sheet of fetal liver mesothelial cells (FL-MCs) to prevent postoperative adhesion in a novel mouse model. Besides adhesion, repeated hepatectomy has another serious problem; although the liver has a remarkable ability to regenerate, the recovery of liver mass and function of the remnant liver after multiple repeated hepatectomy is limited. The FL-MC cell sheet enhances proliferation of hepatocytes after hepatectomy by providing growth factors for hepatocytes. Thus the FL-MC sheet could simultaneously solve the two problems associated with repeated hepatectomy.

In situ forming hydrogel composed of hyaluronate and polygalacturonic acid for prevention of peridural fibrosis

Hyaluronic acid-based hydrogels can reduce postoperative adhesion. However, the long-term application of hyaluronic acid is limited by tissue mediated enzymatic degradation. To overcome this limitation, we developed a polygalacturonic acid and hyaluronate composite hydrogel by Schiff's base crosslinking reaction. The polygalacturonic acid and hyaluronate composite hydrogels had short gelation time (less than 15 s) and degraded by less than 50 % in the presence of hyaluronidase for 7 days. Cell adhesion and migration assays showed polygalacturonic acid and hyaluronate composite hydrogels prevented fibroblasts from adhesion and infiltration into the hydrogels. Compared to hyaluronate hydrogels and commercial Medishield™ gels, polygalacturonic acid and hyaluronate composite hydrogel was not totally degraded in vivo after 4 weeks. In the rat laminectomy model, polygalacturonic acid and hyaluronate composite hydrogel also had better adhesion grade and smaller mean area of fibrous tissue formation over the saline control and hyaluronate hydrogel groups. Polygalacturonic acid and hyaluronate composite hydrogel is a system that can be easy to use due to its in situ cross-linkable property and potentially promising for adhesion prevention in spine surgeries.

A multicentre, randomised, controlled trial to assess the safety, ease of use, and reliability of hyaluronic acid/carboxymethylcellulose powder adhesion barrier versus no barrier in colorectal laparoscopic surgery

Background

Intra-peritoneal adhesions are frequent following abdominal surgery and are the most common cause of small bowel obstructions. A hyaluronic acid/carboxymethylcellulose (HA/CMC) film adhesion barrier has been shown to reduce adhesion formation in abdominal surgery. An HA/CMC powder formulation was developed for application during laparoscopic procedures.

Methods

This was an exploratory, prospective, randomised, single-blind, parallel-group, Phase IIIb, multicentre study conducted at 15 hospitals in France to assess the safety of HA/CMC powder versus no adhesion barrier following laparoscopic colorectal surgery. Subjects ≥18 years of age who were scheduled for colorectal laparoscopy (Mangram contamination class I‒III) within 8 weeks of selection were eligible, regardless of aetiology. Participants were randomised 1:1 to the HA/CMC powder or no adhesion barrier group using a centralised randomisation list. Patients assigned to HA/CMC powder received a single application of 1 to 10 g on adhesion-prone areas. In the no adhesion barrier group, no adhesion barrier or placebo was applied. The primary safety assessments were the incidence of adverse events, serious adverse events, and surgical site infections (SSIs) for 30 days following surgery. Between-group comparisons were made using Fisher’s exact test.

Results

Of those randomised to the HA/CMC powder (n = 105) or no adhesion barrier (n = 104) groups, one patient in each group discontinued prior to the study end (one death in each group). Adverse events were more frequent in the HA/CMC powder group versus the no adhesion barrier group (63% vs. 39%; P <0.001), as were serious adverse events (28% vs. 11%; P <0.001). There were no statistically significant differences between the HA/CMC powder group and the no adhesion barrier group in SSIs (21% vs. 14%; P = 0.216) and serious SSIs (12% vs. 9%; P = 0.38), or in the most frequent serious SSIs of pelvic abscess (5% and 2%; significance not tested), anastomotic fistula (3% and 4%), and peritonitis (2% and 3%).

Conclusions

This exploratory study found significantly higher rates of adverse events and serious adverse events in the HA/CMC powder group compared with the no adhesion barrier group in laparoscopic colorectal resection.

Trial registration

ClinicalTrials.gov NCT00813397. Registered 19 December 2008.

The neurokinin 1 receptor regulates peritoneal fibrinolytic activity and postoperative adhesion formation

BACKGROUND

Intra-abdominal adhesions are a common source of postoperative morbidity. Previous studies in our laboratory have shown that a neurokinin 1 receptor antagonist (NK-1RA) reduces abdominal adhesion formation and increases peritoneal fibrinolytic activity. However, the cellular pathway by which the antagonist exerts its effects is unclear, as cultured peritoneal mesothelial cells exposed to the NK-1RA show increases in fibrinolytic activity despite having very low expression of neurokinin 1 receptor (NK-1R) messenger RNA and protein. Our aim was to determine whether the NK-1R plays an essential role in the adhesion-reducing effects of the NK-1RA, or if the NK-1RA is acting independently of the receptor.

METHODS

Homozygous NK-1R knockout mice and age matched wild-type mice underwent laparotomy with cecal cautery to induce adhesions. At the time of surgery, mice received a single intraperitoneal dose of either NK-1RA (25 mg/kg) or saline alone. Adhesion severity at the site of cecal cautery was assessed on postoperative day 7. In a separate experiment, peritoneal fluid was collected from wild type and NK-1R knockout mice 24 h after laparotomy with cecal cautery and administration of either NK-1RA or saline. Tissue plasminogen activator levels, representative of total fibrinolytic activity, were then measured in peritoneal fluid.

RESULTS

In wild-type mice, NK-1RA administration significantly decreased adhesion formation compared with saline controls. Among the NK-1R knockout mice, there was no significant reduction in adhesion formation by the NK-1RA. Fibrinolytic activity increased 244% in wild-type mice administered NK-1RA compared with saline controls; however, the NK-1RA did not raise fibrinolytic activity above saline controls in NK-1R knockout mice.

CONCLUSIONS

These data indicate that the NK-1R mediates the adhesion-reducing effects of the NK-1RA, in part, by the upregulation of peritoneal fibrinolysis, and suggest that the NK-1R is a promising therapeutic target for adhesion prevention.

Histone deacetylase inhibitors decrease intra-abdominal adhesions with one intraoperative dose by reducing peritoneal fibrin deposition pathways

BACKGROUND

We previously demonstrated that postoperative peritoneal injury and inflammation contribute to adhesiogenesis. Recent evidence suggests that in addition to their role of interfering with the acetylation status of nuclear histone proteins, histone deacetylase inhibitors (HDACIs) including valproic acid (VPA) can target nonhistone proteins to resolve inflammation and modulate immune cells. We hypothesized that HDACIs could reduce adhesions.

METHODS

Seventy-two rats underwent laparotomy with creation of 6 peritoneal ischemic buttons to induce adhesions. A single intraperitoneal (IP) dose of 50 mg/kg VPA was administered intraoperatively, whereas controls received vehicle. To evaluate the timing, 25 rats underwent ischemic button creation with either an intraoperative or a delayed IP dose of VPA at 1, 3, or 6 hours postoperatively. On postoperative day 7, adhesions were quantified. To investigate mechanisms, ischemic buttons were created in 24 rats and either VPA or saline was administered in 1 intraoperative dose. At 3 or 24 hours later, peritoneal fluid was collected and fibrinolytic activity measured. Alternatively, button tissue was collected 30 minutes postoperatively to measure tissue factor, fibrinogen, and vascular endothelial growth factor (VEGF) by real-time polymerase chain reaction or Western blot.

RESULTS

A single intraoperative dose of VPA reduced adhesions by 50% relative to controls (P < .001). Delayed dosing did not reduce adhesions. In operated animals, peritoneal fibrinolytic activity was not different between groups. Tissue factor mRNA was downregulated by 50% (P = .02) and protein by 34% (P < .01) in animals administered VPA versus saline. VPA decreased fibrinogen protein by 56% and VEGF protein by 25% compared with saline (P = .03).

CONCLUSION

These findings suggest that VPA rapidly reduces the extravasation of key adhesiogenic substrates into the peritoneum. A single, intraoperative intervention provides an ideal dosing strategy and indicates an exciting new role for HDACIs in adhesion prevention.

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.

Preventing intra-abdominal adhesions with a sodium hyaluronate carboxymethylcellulose membrane enabled visualization of hepatic microcirculation

We aimed to evaluate whether using sodium hyaluronate carboxymethylcellulose membrane (Seprafilm™) can facilitate assessment of hepatic microcirculation via orthogonal polarization spectroscopy (OPS) by preventing intra-abdominal adhesions and whether Seprafilm™ as a foreign material can evoke local or systemic inflammatory reactions. After the right median hepatic vein was ligated, rats received either placement of Seprafilm™ or untreated with observation of 1 or 4 weeks (n = 6/group). Hepatic microcirculation was visualized. Systemic and local inflammatory reactions were evaluated by blood count, histology and immunohistochemical staining for CD68. Seprafilm™ significantly (P < 0.05) prevented intra-abdominal adhesion formation compared to non-Seprafilm™ groups (adhesion score: 0 vs 1.3 ± 0.5 at POW1 and 0.3 ± 0.5 vs 3.5 ± 1.4 at POW4). Placement of Seprafilm™ provided sufficient liver surface for acquisition of OPS videos during the harvest procedure. Adhesiolysis in non-Seprafilm™ groups prevented visualization of hepatic microcirculation. A severe local foreign body reaction with formation of a "fibrin-like" membrane containing CD68-positive inflammatory histiocytic cells and mesothelial cells was observed in Seprafilm™ groups even at POW4. Use of Seprafilm™ conferred visualization of hepatic microcirculation after long term observation in experimental setting. In clinical situation, we would suggest being very cautious in immuno-compromised patients because of an ongoing local foreign body reaction caused by Seprafilm™.

Trehalose does not affect the functions of human neutrophils in vitro

PURPOSE

Trehalose, naturally occurring disaccharide, has been reported to prevent postoperative abdominal adhesions in animal models. We investigated whether trehalose affects the function of human polymorphonuclear neutrophils (PMNs) in vitro to assess the feasibility of its clinical application as an anti-adhesive barrier.

METHODS

Human PMNs were obtained from 17 healthy volunteers. Escherichia coli and Staphylococcus aureus were used for the bacterial infection model, whereas lipopolysaccharide (LPS) and interleukin (IL)-1β were used for inflammation induction model. The PMN phagocytosis rates of bacteria and apoptosis/necrosis were assessed on trehalose, maltose, and control media. Cytokines; namely, tumor necrosis factor-α, IL-1α, IL-1Ra, IL-6, and IL-8; and PMN-elastase were measured on each medium in both models.

RESULTS

There were no significant differences in the phagocytosis rates, apoptosis/necrosis rates, or levels of all cytokines or PMN-elastase among the three media in the bacterial infection model. There were also no significant differences in the levels of all cytokines and PMN-elastase among the three media in the IL-1β inflammation induction model. PMN-elastase was lower in trehalose and maltose medium after LPS stimulation, at 3 and 24 h.

CONCLUSIONS

Our results suggest that trehalose does not affect the cellular function, cytokine production, or release of PMN-elastase of human PMNs in an in vitro bacterial infection model.

Prevention of postsurgical adhesions using an ultrapure alginate-based gel

Background

Postoperative adhesion formation is a common consequence of abdominal surgery, and constitutes a major source of morbidity and mortality. This study evaluated an ultrapure alginate-based antiadhesive barrier gel.

Methods

Experiments were performed in a rat model with caecal abrasion and peritoneal side wall excision. The primary endpoint was the incidence of adhesions at 14 days after surgery. In experiment 1 (24 rats), animals treated with alginate gel were compared with controls that had no antiadhesive barrier. In experiment 2 (42 rats), alginate gel was compared with sodium hyaluronate carboxymethyl cellulose (HA/CMC) membrane and with no antiadhesive barrier. To check for any remote action of the gel, in experiment 3 (45 rats) application of alginate gel to the ipsilateral versus contralateral side of injury was compared with no antiadhesive barrier.

Results

In experiment 1, ultrapure alginate gel reduced the incidence of adhesions from eight of 12 in control animals to one in 12 (P = 0·009). Tissue healing assessed by histology was similar in both groups. In experiment 2, ultrapure alginate gel and HA/CMC membrane showed similar antiadhesive effectiveness, reducing the incidence of adhesions from ten of 14 rats in the control group to three of 14 (P = 0·021) and two of 14 (P = 0·006) respectively. In experiment 3, ultrapure alginate gel reduced the incidence of adhesions at the site of direct application (1 of 15) compared with controls (13 of 15; P = 0·001), but not if applied remotely (9 of 15; P = 0·214).

Conclusion

Ultrapure alginate gel decreased the incidence of postoperative adhesion formation in this rat model.

New hepatectomy-induced postoperative adhesion model in rats, and evaluation of the efficacy of anti-adhesion materials

PURPOSE

Repeated hepatic resections are not uncommon during the surgical management of liver tumors. Postoperative adhesions induced by hepatectomies can have a significant negative impact on subsequent surgeries. We recently developed a new hepatectomy-induced postoperative adhesion animal model to evaluate the anti-adhesion efficacy of commercially available sheet materials (Seprafilm(®) and Interceed(®)) and the recently reported hyaluronan-based in situ cross-linkable hydrogels.

METHODS

The median lobe (ML) and the left lateral lobe (LLL) of the liver (approximately 70 % of the total liver) of 43 male Sprague-Dawley rats were resected based on the classical procedure; anti-adhesion materials were then applied. A relaparotomy was performed 1 week later to evaluate the adhesions and histopathological findings.

RESULTS

The rats without the application of anti-adhesion materials (n = 14) showed the most severe adhesions (grade 3) between the cut surface of the liver and the small bowel or omentum. All the barrier materials produced slight anti-adhesion effects. Adhesions between the liver surface and the diaphragm and adhesions around the hepatic hilum were less severe, but were not remarkably reduced, by the anti-adhesion materials.

CONCLUSION

We successfully established a new hepatectomy-induced animal adhesion model, which may be useful for the development of new anti-adhesion materials.

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.

Remote efficacy for two different forms of hyaluronate-based adhesion barriers

BACKGROUND

Chemically modified sodium hyaluronate and carboxymethylcellulose (HA/CMC) membrane clinically reduces adhesion formation following surgery but was not designed for laparoscopic use. HA/CMC powder of identical chemical composition has been developed to allow for application laparoscopically. We compared the adhesion reduction efficacy of HA/CMC powder and film when applied directly to or remote from sites of surgical trauma. We also investigated the effect of the powder on wound healing.

MATERIALS AND METHODS

Two animal models of adhesion formation were used to evaluate efficacy: a rat peritoneal sidewall defect model and a rabbit cecal abrasion/sidewall defect model. The products were applied directly to the defect or the contralateral sidewall. Adhesions were examined seven days after surgery. In a separate study, the effect of the powder on healing was evaluated at 5, 7, and 28 days using a rat incisional wound strength model.

RESULTS

HA/CMC powder and film, when applied directly to the peritoneal defect, significantly reduced adhesions relative to the untreated control in both models. Remote applications of HA/CMC powder also reduced adhesions. In contrast, remote applications of HA/CMC film had no effect. HA/CMC powder did not significantly alter incisional wound strength at any of the timepoints tested.

CONCLUSION

In our preclinical models, HA/CMC powder had similar adhesion reduction efficacy to HA/CMC film when applied directly to sites of trauma. In addition, HA/CMC powder reduced adhesions remote from the application site. Importantly, HA/CMC powder did not impair incisional wound healing. On the basis of these results, future investigation of HA/CMC powder is warranted.

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.

Seprafilm® adhesion barrier: (1) a review of preclinical, animal, and human investigational studies

The aim of this study was to provide a single site resource for investigators, clinicians, and others seeking preclinical, animal, and human investigational studies concerning the postsurgical, anti-adhesion barrier Seprafilm™ (Genzyme Corporation, Cambridge, MA). All published preclinical, animal, human extra-abdominal research as of July 2011 have been summarized and included in this document. Searches of Medline and EMBASE Drugs and Pharmaceuticals databases were conducted for original preclinical, animal, and human extra-abdominal studies involving Seprafilm. Preclinical, animal, and extra-abdominal human investigational studies are the study selection for this manuscript. Intraabdominal use is discussed in the accompanying manuscript. Data extraction includes systematic manuscript review. Summary of preclinical, animal, and extra-abdominal human investigational use of Seprafilm by surgical discipline were gathered for data synthesis. The clinical use of Seprafilm, which was approved by the FDA for intra-abdominal procedures, is supported by preclinical and animal studies relating to general surgical and obstetrical/gynecological applications. Findings from preclinical, animal, and human investigational studies at other sites throughout the body raises the potential for additional human clinical trials to assess efficacy and safety following surgical procedures at non-abdominal locations.

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.

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.

Gynecologic use of Sepraspray Adhesion Barrier for reduction of adhesion development after laparoscopic myomectomy: a pilot study

OBJECTIVE

To assess the safety and efficacy of Sepraspray Adhesion Barrier (a modified hyaluronic acid and carboxymethylcellulose powder) after laparoscopic surgery, in view of both the high efficacy of Seprafilm Adhesion Barrier in reducing postoperative adhesions after open surgical procedures and the difficulty with laparoscopic delivery.

DESIGN

Multicenter, randomized, reviewer-blinded trial.

SETTING

Reproductive endocrinology and infertility clinics.

PATIENT(S)

Women undergoing laparoscopic myomectomy for indications including infertility.

INTERVENTION(S)

Randomization to treatment with (n = 21) or without (n = 20) Sepraspray Adhesion Barrier.

MAIN OUTCOME MEASURE(S)

Postoperative adhesions development was assessed at early second-look laparoscopy. Adhesions were scored using the modified American Fertility Society scoring system.

RESULT(S)

Surgical procedure duration length was 99 versus 102 minutes in the control versus Sepraspray Adhesion Barrier groups, respectively, with the median number of fibroids removed being two in each group and corresponding fibroid weights of 134 ± 103 versus 113 ± 161 g, respectively. Adhesions scores increased in both the control and Sepraspray Adhesion Barrier groups, with larger although nonstatistically significant increases noted in control subjects when evaluating for the anterior uterus, the posterior uterus, and the entire uterus.

CONCLUSION(S)

Laparoscopic application of Sepraspray Adhesion Barrier after myomectomy in this pilot study was associated with a trend toward a reduction in postoperative adhesion development, as well as an encouraging safety profile. Further evaluation is warranted.

CLINICAL TRIAL NUMBER

Sepraspray Adhesion Barrier #NCT00624930.

An assessment of the effects of a hyaluronan-based solution on reduction of postsurgical adhesion formation in rats: a comparative study of hyaluronan-based solution and two film barriers

BACKGROUND

Intra-abdominal application of anti-adhesive barriers may reduce the extent and severity of postoperative adhesions. This study was designed to compare the effectiveness of a sprayable liquid barrier (a mixed solution of sodium hyaluronate and carboxymethylcellulose) with two conventional sheets.

METHODS

Eighty male Sprague Dawley rats underwent laparotomy with subsequent multiple intestinal wall abrasions and abdominal wall injury. Afterwards, sodium hyaluronate and carboxymethylcellulose (HA-CMC) solutions were intraperitoneally sprayed or a film barrier of either oxidized regenerated cellulose (ORC) or polylactic acid (PA) was placed under the incision. At postoperative d 21, the rats underwent relaparotomy and complete adhesiolysis. Three investigators, who were blind to the group assignment, scored the extent of adhesion formation and resected specimens for histologic examination of fibrosis and inflammation. Expression profiles of parameters as mediators (macrophages [CD68]) in cellular inflammation response were analyzed.

RESULTS

Mean adhesion scores in rats that received HA-CMC solution (7.6±2.3) and ORC membrane (8.1±2.2) were lower than in rats that received PA film (10.7±2.5) and the control group (11.2±2.6) (P<0.05 for each comparison). In addition, there were significantly fewer adhesions located between large and small intestine in the HA-CMC solution group than in the control and each of the film barrier groups (P<0.05 for each comparison).

CONCLUSIONS

This study suggests that both HA-CMC solution and ORC membrane decrease the overall incidence of postoperative adhesions. However, the mixed solution of HA-CMC appeared to be superior to ORC membrane because this sprayable solution is easy to use and suitable for site-specific adhesion prevention after multifocal bowel trauma.