Effects of five different barrier materials on postsurgical adhesion formation in the rat

Function of poly (lactic-co-glycolic acid) nanofiber in reduction of adhesion bands

BACKGROUND

In this study, we investigated the anti-adhesive and anti-inflammatory effects of electrospun nanofibrous membranes made of polycaprolactone (PCL), poly-L-lactide (PLLA), poly (lactic-co-glycolic acid) (PLGA), and polyethersulfune (PES) in comparison with the oxidized-regenerated cellulose (Interceed).

MATERIALS AND METHODS

Using an adhesion induction model in mice, the membranes were sutured between the abdominal wall and peritoneum after surgical operation to reveal the best membrane for prevention of postoperative adhesion bands using two scoring adhesion systems.

RESULTS

Compared with other membranes, PLGA, PCL, and Interceed membranes showed a greater ability to reduce adhesions. The lowest level of inflammation in adhesive tissues as well as cell attachment in vitro was detected for PLGA nanofibrous membranes.

CONCLUSIONS

These results suggested that in considering the FDA approved polymers, nanofibrous membranes prepared from PLGA exhibited the highest efficacy for the prevention of postoperative adhesion bands and hold promising potential for application as a new anti-adhesive agent.

Effects of solid hyaluronic acid film on postoperative fibrous scar formation after strabismus surgery in animals

PURPOSE

The purpose of this study was to investigate the inhibitory effect of solid hyaluronic acid-carboxymethylcellulose film on the formation of wound adhesion after strabismus surgery on rabbit eyes.

METHODS

The authors performed strabismus surgery on rabbit eyes with hyaluronic acid film applied under and above the muscles. Histological examination was performed 90 days postoperatively using Masson trichrome staining. The length of adhesion tissues in the operated area was quantitatively compared between film-treated and control eyes.

RESULTS

Hyaluronic acid film significantly prevented the formation of adhesions between muscle, conjunctiva, and sclera after strabismus surgery (t test, P < .05).

CONCLUSION

The current results indicate that hyaluronic acid film can inhibit the formation of postoperative adhesion around conjunctiva, muscle, and sclera to some extent. The authors conclude that this substance offers potential benefits for ophthalmic surgery, not only with strabismus surgery but also procedures such as scleral buckle.

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.

Preventing intraperitoneal adhesions with atorvastatin and sodium hyaluronate/carboxymethylcellulose: a comparative study in rats

OBJECTIVES

The aim of this study was to compare the effectiveness of atorvastatin with the sodium hyaluronate/carboxymethylcellulose (HA/CMC, Seprafilm; Genzyme; Genzyme Biosurgery Corporation, Cambridge, MA) in preventing postoperative intraperitoneal adhesion formation in rats.

METHODS

Sixty Wistar rats underwent a laparotomy, and adhesions A were induced by cecal abrasion. The animals were divided into 4 groups: group 1, control A; group 2, (A + atorvastatin); group 3, (A + HA/CMC), and group 4, (A + atorvastatin + HA/CMC). The atorvastatin (groups 2 and 4) and HA/CMC (groups 3 and 4) were administered intraperitoneally before the abdominal wall was closed. After 14 days, adhesions were classified by 2 independent surgeons.

RESULTS

The adhesion scores (mean +/- standard deviation) for groups 1, 2, 3, and 4 were 2.93 +/- .59, 1.85 +/- 1.07, 1.80 +/- .86, and 1.93 +/- .70, respectively. The differences in adhesion scores among all 3 preventive groups (groups 2, 3, and 4) were statistically significant when compared with the control group (P = .005, P = .002, and P = .009, respectively).

CONCLUSIONS

These data suggest that atorvastatin, administered intraperitoneally, is as effective as HA/CMC without an expectable additive effect in preventing postoperative adhesions in rats.

Surface modification of silk fibroin with poly(ethylene glycol) for antiadhesion and antithrombotic applications

Silk fibroin film surfaces were PEGylated by reaction with cyanuric chloride-activated poly(ethylene glycol) (PEG). Reactions with different concentrations of activated PEG generated films with PEG graft densities from 0.02 to 0.4 mg per square cm of silk fibroin. Increased PEGylation resulted in increased hydrophilicity as analyzed by contact angle, and a smoother morphology based on scanning electron microscopy. Increased PEGylation decreased human IgG adsorption and decreased the attachment and proliferation of human fibroblasts over two weeks. Increased concentration of PEG on the silk fibroin surfaces also decreased the proliferation of human mesenchymal stem cells and inhibited human platelet attachment. Surface PEGylated silk fibroin films could be useful antiadhesion and antithrombotic materials for biomedical applications when considered along with the unique mechanical and tailorable degradation profiles of silk fibroin.

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.

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.

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.

Prevention of peritoneal adhesions by intraperitoneal administration of vitamin E and human amniotic membrane

BACKGROUND

Our objective was to evaluate the comparative effectiveness of intraperitoneally administered vitamin E and human amniotic membrane in preventing postoperative intraperitoneal adhesion formation.

MATERIAL AND METHODS

75 Wistar-albino rats were separated into 5 groups: Group 1 (control), Group 2 (intraperitoneal olive oil, the diluent of vitamin E), Group 3 (Intraperitoneal vitamin E diluted in olive oil), Group 4 (Amniotic membrane group) and Group 5 (Amniotic membrane and Intraperitoneal vitamin E diluted in olive oil). The same experimental method, consisting of cecal abrasion and ligature of the adjacent parietal peritoneum, was used in all rats to produce adhesions. Relaparotomy was performed on the 15th postoperative day. intra-abdominal adhesions were scored according to macromorphological characteristics and adhesion-carrying tissues underwent standard histologic examination. Inflammation, vascularization and fibrosis in granulation sites were graded in all samples. The results were analyzed using a Mann-Whitney-U test.

RESULTS

In terms of inflammation, neovascularization and fibrosis scores obtained by histology and macromorphologic adhesion scores. There were no significant differences between Groups 1 and 2 (p=0.176). The results of Groups 3, 4 and 5 showed a significant difference when compared with both Group 1 and 2 (p=0.001). The difference between Groups 3, 4 and 5 were not significant with respect to these 4 parameters.

CONCLUSION

Intraperitoneal vitamin E and amniotic membrane treatment were both effective in the prevention of peritoneal adhesions. The combination of these agents did not produce a synergistic effect. Easy applicability of the intraperitoneal administration of vitamin E was its major advantage.

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

OBJECTIVE

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

MATERIAL AND METHODS

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

RESULTS

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

CONCLUSION

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

Human peritoneal membrane reduces the formation of intra-abdominal adhesions in ventral hernia repair: experimental study in a chronic hernia rat model

BACKGROUND

Adhesions leading to intestinal obstructions and fistulae are severe complications related to the intraperitoneal placement of synthetic meshes. This study evaluated the efficacy of human peritoneal membrane (HPM) in a chronic hernia repair rat model as an anti-adhesive solution for preventing the development of intra-abdominal adhesions.

MATERIALS AND METHODS

The mechanical properties of HPM and human fascia lata (HFL) were evaluated prior to in vivo implantation. Twenty rats underwent midline laparotomy, which led to the development of chronic hernias 28 d later. Then, animals underwent incisional hernia repair in an underlay fashion (n=5/mesh group) with compressed poly(tetra-fluoro-ethylene) (cPTFE), onto which HPM or HFL were affixed pre-repair, along with two additional controls. The extent and tenacity of intra-abdominal adhesions were determined through qualitative gross evaluations and quantitative tensiometry at 30 d post-repair. The host tissue response was evaluated histologically.

RESULTS

In hydrated state, the elastic properties of HPM were superior to HFL. Repairs with HPM had significantly less surface area covered by adhesions, with significantly lower tenacity compared with all other groups. Furthermore, intra-abdominal adhesions developed in the presence of HPM were associated with omentum only, and were distributed around the perimeter of the exposed cPTFE. HPM served as an active tissue remodeling template, replacing the traditional foreign body encapsulation with an anatomically and physiologically superior outcome.

CONCLUSIONS

HPM significantly reduces the extent and tenacity of intra-abdominal adhesion formation, and represents a bioprosthetic template that encourages structural and functional neo peritonealization.

Preventing intraperitoneal adhesions with vitamin E and sodium hyaluronate/carboxymethylcellulose: a comparative study in rats

PURPOSE

To compare the effectiveness of intraperitoneally administered vitamin E with the sodium hyaluronate/carboxymethylcellulose membrane (HA/CBMC) in preventing postoperative intraperitoneal adhesion formation.

METHODS

Sixty Wistar rats underwent a laparotomy and adhesions were induced (IA). The animals were divided into four groups: group 1, control (IA); group 2 (IA + Vitamin E): group 3 (IA+HA/CBMC) and group 4 (IA+ Vitamin E + HA/CBMC). The Vitamin E (groups 2 and 4) and HA/CBMC (groups 3 and 4) were administered intraperitoneally before the abdominal wall was closed. After 30 days, adhesions were classified by an independent surgeon.

RESULTS

Three animals died; one from group 3 and two from group 4. All control animals had substantial adhesions compared with unsubstantial adhesions observed in 11/15 in group 2 (P = 0.000), 11/14 in group 3 (P = 0.001), and 10/13 in group 4 (P = 0.000).

CONCLUSION

Vitamin E, administered intraperitoneally, is as effective as HA/CBMC in preventing postoperative adhesions.

Reduction of postsurgical adhesions in a rat model: a comparative study

BACKGROUND

Adhesion formation after peritoneal surgery is a major cause of postoperative bowel obstruction, infertility, and chronic pelvic pain. In this study, we compared the possible individual effects of phosphatidylcholine (PC), Seprafilm II, and tissue plasminogen activator (t-PA) and the combined effects of phosphatidylcholine and t-PA on postoperative adhesion formation in a rat surgical model.

MATERIALS AND METHODS

A total of 50 Wistar male rats underwent median laparotomy and standardized abrasion of the visceral and parietal peritoneum. phosphatidylcholine, Seprafilm II, and t-PA alone and phosphatidylcholine and t-PA in combination were applied intraperitoneally at the end of the surgical procedure. Seven days after surgery, a relaparotomy was performed for adhesion grading and histopathological examination.

RESULTS

A comparison of adhesion stages demonstrated a significant difference between the control group and the study groups (p<0.001). The adhesion grade of the combined treatment group was statistically different from that of the other groups (p<0.05). In the t-PA group and the combined group, six and two rats, respectively, developed hematomas locally on the cecum.

CONCLUSIONS

PC, t-PA, and Seprafilm II used individually reduced the adhesion grade. The t-PA and phosphatidylcholine combination was most effective in reducing adhesion formation. On the other hand, usage of t-PA alone or in combination may increase risk of bleeding. More detailed studies are needed, and future studies on the efficacy of a material for decreasing adhesion formation should include a comparison of several control materials in the same model.

Comparison of intraperitoneal honey and sodium hyaluronate-carboxymethylcellulose (Seprafilm) for the prevention of postoperative intra-abdominal adhesions

BACKGROUND

Abdominal surgery can lead to postoperative intra-abdominal adhesions (PIAAs) with significant morbidity and mortality. This study compares the use of honey with a standard bioresorbable membrane (SEPRAFILM) to prevent the formation of PIAAs in rats.

METHODS

Thirty rats underwent laparotomy, and PIAAs were induced by scraping the cecum. The animals were divided into three groups, each containing ten rats. Group 1 (control) represented the cecal abrasion group, with no intraperitoneal administration of any substance. Group 2 (honey group) underwent cecal abrasion and intraperitoneal administration of honey. Group 3 (Seprafilm group) underwent cecal abrasion and intraperitoneal Seprafilm application.

RESULTS

Group 1 exhibited higher adhesion scores for adhesions between the abdominal wall and the organs. Groups 2 and 3 had decreased adhesive attachments to the intra-abdominal structures. Compared to group 1, the incidence of adhesion formation was lower in both group 2 (p=0.001) and group 3 (p=0.001). The incidence of fibrosis was also lower in group 2 (p=0.016) and group 3 (p=0.063) compared to group 1. There was no significant difference between the histopathological fibrosis scores for the rats in group 2 and those in group 3 (p= 0.688).

CONCLUSION

This study suggests that both honey and Seprafilm decrease the incidence of PIAAs in the rat cecal abrasion model. Although the mechanism of action is not clear, intraperitoneal administration of honey reduced PIAAs. The outcome of this study demonstrates that honey is as effective as Seprafilm in preventing PIAAs.

The effect of anti-adhesive packing agents in the middle ear of guinea pig

BACKGROUND & OBJECTIVE

The presence of adhesions after middle ear surgery is not uncommon. Fibrosis can cause conductive hearing loss and it contributes to retraction of the tympanic membrane in the post-surgery patient. The purpose of this study was to evaluate the anti-adhesive effect of Seprafilm and MeroGel in the abraded mucosa of a guinea pig's middle ear.

MATERIALS AND METHODS

Fifteen pathogen-free adult male albino guinea pigs weighing 250-300g each were used. Under an aseptic condition, the middle ear mucosa was abraded using a pick through a myringotomy incision. Seprafilm, MeroGel and Gelfoam, respectively, were then packed into guinea pigs' middle ear cavities. Auditory brainstem responses (ABRs) were assessed preoperatively and 3 weeks after operation.

RESULTS

The ABR results at postoperative week 3 showed no statistically significant difference for the myringotomy and postpacking, except for the MeroGel packing. However, there was no significant threshold on the 6 weeks' postoperative ABR. The Gelfoam group demonstrated extensive fibrosis and adhesion within the bulla cavity. The Seprafilm and MeroGel groups showed no adhesion in the middle ear cleft after abrasion of the mucosa.

CONCLUSION

From these results, we suggest the use of Seprafilm and MeroGel to improve the results of otosurgery.

Electrospun matrices made of poly(α-hydroxy acids) for medical use

Biomaterials are widely used in diverse applications as substances, materials or important elements of biomedical devices. Biodegradable polymers, both natural and synthetic, have been utilized in applications in which they act as temporary substitutes. Poly(α-hydroxy acids), especially lactic acids and glycolic acid and their copolymers with ε-caprolactone, are the most widely known and used among all biodegradable polymers. They degrade in vivo into safe end products mainly by hydrolysis in a few weeks to several months, depending on several factors, including molecular structure/morphology, average molecular weight, size and shape. They are processed into tailor-made materials for diverse applications, although mainly for soft and hard tissue repair. Electrospinning is a method of producing nanofibers and nonwoven matrices from their solutions and melts. Several factors affect fiber diameter and resulting nonwoven structures/morphologies. Recently, electrospun matrices made of lactic acids, glycolic acid and ε-caprolactone homo- and co-polymers have been attracting increasing attention for fabrication of novel materials for medical use. This review briefly describes poly(α-hydroxy acids) and the elecrospinning process, and gives some selected recent applications of electrospun matrices made from these polymers.

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.

In vivo performance of antibiotic embedded electrospun PCL membranes for prevention of abdominal adhesions

The aim of this study was to prepare nonwoven materials from poly(epsilon-caprolactone) (PCL) and their antibiotic containing forms by electrospinning, so as to prevent postsurgery induced abdominal adhesions in rats. epsilon-Caprolactone was first polymerized by ring-opening polymerization, and then it was processed into matrices composed of nanofibers by electrospinning. A model antibiotic (Biteral) was embedded within a group of PCL membranes. In the rat model, defects on the abdominal walls in the peritoneum were made to induce adhesion. The plain or antibiotic embedded PCL membranes were implanted on the right side of the abdominal wall. No membrane implantation was made on the left side of the abdominal wall that served as control. Macroscopical and histological evaluations showed that using these barriers reduces the extent, type, and tenacity of adhesion. The antibiotic embedded membranes significantly eliminated postsurgery abdominal adhesions, and also improved healing.

Innovative barriers for peritoneal adhesion prevention: liquid or solid? A rat uterine horn model

OBJECTIVE

To compare the effects of solid barriers (PDLA membrane and foil, Interceed), innovative barrier solutions (Adept and Hyalobarrier Gel, phospholipid emulsion), and Ringer's lactate solution in preventing postsurgical peritoneal adhesions in the rat.

DESIGN

Prospective, randomized experimental study.

SETTING

Rat model in an academic research environment.

ANIMAL(S)

Female, nonpregnant Wistar rats.

INTERVENTION(S)

Standardized surgical injuries were applied to the parietal and visceral peritoneum and the uterine horns. The barrier agents were applied and the wound was closed. A second-look laparoscopy was performed 31 days after surgery to assess adhesion formation.

MAIN OUTCOME MEASURE(S)

Severity and extent of adhesion formation assessed using a multidimensional adhesion scoring system.

RESULT(S)

Significantly fewer postsurgical adhesions were seen after treatment with Adept, Hyalobarrier Gel, Interceed, PDLA membrane, and phospholipid emulsion than after Ringer's lactate solution. Severe, clinically relevant adhesions were not observed after Hyalobarrier Gel and in only one animal after Adept.

CONCLUSION(S)

Both solid and liquid barriers can prevent adhesions. Hydroflotation formulas, such as Adept and Hyalobarrier Gel, avoid suture-induced adhesions, are easy to use, and their protective effects are evenly distributed. They are suitable for adhesion prevention after multifocal trauma in rats, and require further testing in the everyday clinical situation.

Hyaluronic Acid/Carboxymethylcellulose Membrane Barrier versus Taurolidine for the Prevention of Adhesions to Polypropylene Mesh

BACKGROUND

A hyaluronic acid/carboxymethylcellulose (HA/CMC) membrane is an effective measure to prevent polypropylene mesh induced adhesions. We hypothesized that taurolidine 2% solution might be a cost-effective alternative to decrease adhesion formation.

MATERIALS AND METHODS

Twenty-four rats were randomized into three groups: mesh alone (group 1), mesh + taurolidine 2% (group 2), and mesh + HA/CMC (group 3). Polypropylene mesh (4 cm2) was used to repair surgically induced anterior abdominal wall defects. Taurolidine 2%or a HA/CMC membrane was used as an antiadhesive measure. The animals were sacrificed 6 weeks after the operation, and adhesions to the prosthetic material were evaluated with digital image analysis.

RESULTS

Group 1 (mesh alone) had the highest adhesion ratio (58.5 +/- 4.8%) compared with groups 2 and 3 (p < 0.05). The differences between groups 2 (mesh + taurolidine 2%; adhesion ratio 42.9 +/- 1.6%) and 3 (mesh + HA/CMC; adhesion ratio 40.3 +/- 3.0%) were not significant (p > 0.05).

CONCLUSIONS

The animals of both treatment groups (2 and 3) had lower adhesion ratios compared with the controls (group 1). In particular, the HA/CMC membrane did not present with a superior antiadhesive effect compared with taurolidine. Therefore, taurolidine is a cost-effective alternative to HA/CMC membranes when a polypropylene mesh is used in direct contact with the abdominal viscera.

Comparative dural closure techniques: a safety study in rats

BACKGROUND

Some neurosurgical procedures have high morbidity and mortality rates due to cerebrospinal fluid (CSF) fistula development, particularly when dural defects are in relatively inaccessible areas or surrounded by friable dura. We used a rat model to test 4 different dural closure techniques to determine which one was significantly superior for achieving a watertight dural closure with minimal harm to brain tissue.

METHODS

The rats were randomly divided into 2 groups. The first group (group A, n = 40) was used to test the strength of the adhesivity for CSF leakage. Histopathologic studies were used to evaluate the granulation tissue between the dura and dural graft. Effects on the brain tissue were studied in the second group (group B, n = 40) where lipid peroxidation was determined. These 2 groups consisted of 5 subgroups: control, methyl metacrylate, n-butyl cyanoacrylate, fibrin glue, and CO(2) laser.

RESULTS

Methyl metacrylate and CO(2) laser techniques were inadequate for stopping dural leakage and had harmful effects on brain tissue. Cerebrospinal fluid leak was observed only in 1 rat in the n-butyl cyanoacrylate subgroup and this result was statistically significant (P = .0005), but lipid peroxidation levels for this material showed that it was not safe for dural closure in case it leaked through the dural defect. The lipid peroxidation levels of the fibrin glue subgroup were not statistically significantly different from the control group (P = .440).

CONCLUSIONS

Fibrin glue was the safest material with a CSF leakage risk that was higher than n-butyl cyanoacrylate (25% vs 12.5%) but acceptable. This study showed no relationship between the CSF leak and histopathologic findings for sealant properties of the tissue adhesives.

Adhesion prevention comparing liquid and solid barriers in the rabbit uterine horn model

OBJECTIVE

The purpose of this study was to assess the ability of four different either solid or fluid barriers to reduce adhesions in an established model of gynecological surgery.

STUDY DESIGN

50 Chinchilla rabbits underwent bilateral deperitonealization and devascularization of the uterine horns (DUH). Afterwards solid membranes of either hyaluronic acid-carboxymethylcellulose (HA-CMC) or lactide-caprolactone-copolymer (LCC) were placed around the injured uterine horns or fluids (icodextrin (ID) or phospholipids (PL)) were intraperitonealy administered. The control group went without protection. After 10 days, adhesions were measured by planimetry.

RESULTS

Phospholipids (median 49.8 mm2) significantly reduced adhesion areas in comparison to all other groups: surgical controls (median 230.6 mm2), HA-CMC (median 194.9 mm2), LCC (median 327.1 mm2), and icodextrin (median 242.1 mm2).

CONCLUSIONS

These results prove the efficacy of phospholipids to reduce primary adhesion formation in the Chinchilla double uterine horn model compared to HA-CMC, LCC and icodextrin. Future clinical studies are recommended.

Topical high molecular weight hyaluronan reduces radicular pain post laminectomy in a rat model

BACKGROUND CONTEXT

A controversy exists about the mechanism of causation of the post-laminectomy pain syndrome. Some believe that epidural scarring, and attendant spinal nerve and nerve root scarring and tethering to the disc or pedicle at the site of surgery contributes to post-laminectomy pain in such patients. However, clinical outcome studies on this question are inconclusive and the assertion remains controversial. Definitive studies to help resolve the question are needed. Previously our laboratory has reported on a preclinical post-laminectomy model that mimics the postoperative proliferative fibrotic response grossly, as well as by biochemical assessment of the collagen content within the spinal canal. The post-laminectomy fibrotic response was attenuated in that study by application of a topical antifibrotic (high molecular weight hyaluronan gel) or by insertion of an absorbable roofing barrier (0.2-mm-thick Macropore sheet material) over the laminectomy defect before wound closure. The question remains of relevance of the attenuation of the fibrotic response to post-laminectomy chronic pain syndromes.

PURPOSE

The purpose of this study is to evaluate the effect of therapeutic attenuation of proliferative scar within the spinal canal post laminectomy on the pain-related behavioral response in a preclinical rat model.

STUDY DESIGN/SETTING

An established L5-L6 rat laminectomy model with a unilateral L5-6 disc injury was employed to assess postoperative proliferative fibrosis of the L5 spinal nerves using quantitative biochemical hydroxyproline assessment of the collagen content in four experimental groups. These observations were correlated with gross descriptions of spinal nerve scarring or tethering. Associated manifestations of a sensory pain-related response in the L5 spinal nerve receptor area of the hind paws was studied using standard tactile allodynia assessment with the von Frey hair technique. The tactile allodynia findings were supplemented by weekly descriptors of behavioral pain manifestations.

METHODS

Bilateral laminectomies at L5 and L6 and a unilateral right disc injury (L5-6) were performed on 35 male adult Sprague-Dawley rats, weighing 400+ grams (approved by the VA Institutional Animal Care Use Committee). The study consisted of four groups: 1) normal nonoperative control; 2) a sham-operated group; 3) an untreated laminectomy-disc injury group; and 4) a laminectomy-disc injury treatment group in which 0.1 cc topical high molecular weight hyaluronan (HMW HA) gel was layered over the dura and into the laminectomy canal before closure. Before animals were entered into the study, they were checked for the presence of abnormal response to the tactile testing procedure of the L5 sensory receptor area. Animals exhibiting anomalous responses were excluded from the study. Behavioral testing for tactile allodynia was performed at weekly intervals post laminectomy beginning at 3 weeks. Pain-related behavior was characterized at weekly intervals. A behavioral test cage with a wire mesh floor allowed for tactile allodynia testing. Graduated von Frey hairs whose stiffness increased logarithmically from 0.41 to 15 g were used for tactile allodynia tests. The animals were killed 8 weeks postoperatively for analysis. The dissected spinal nerve and nerve root specimens were studied biochemically for hydroxyproline content to estimate total collagen in and around the L5 neural structures. Statistical analyses were performed using analysis of variance and a Fisher comparison t test.

RESULTS

The major observations on the untreated preclinical post-laminectomy rat model previously described by this laboratory were confirmed. All untreated animals developed a tail contracture concave toward the right (disc injury side) consistent with asymmetrical lumbar muscle spasm. Only one animal in the HA gel treatment group had a tail contracture. It was of mild degree and occurred in an animal that demonstrated slightly increased right L5 tactile sensitivity. Gross inspection of the dissected specimens demonstrated spinal nerve scarring and tethering to the disc and pedicle greater on the right than the left in untreated animals, findings that were markedly reduced in the treatment group. Collagen content of the L5 spinal nerve and nerve roots with attached scar were significantly lower in the HA gel treatment group than in the untreated laminectomy group (p=.0014). Pain behavioral testing of the L5 receptor area of the right hind paw in the untreated laminectomy group showed markedly increased sensitivity to tactile allodynia testing compared with the corresponding limb of the control group (p=.0001), to the corresponding limb of the sham group (p=.0001), and compared with the HMW HA gel treatment group (p=.0010). Comparisons of the pain behavioral data between the sham and the post-laminectomy HA gel treatment group and the control animals lacked statistical significance.

CONCLUSION

This study supports the concept of a relationship between perineural fibrosis and radicular neuropathy in the model described, and emphasizes the role of disc injury and spinal nerve retraction in the post-laminectomy fibrotic process. Furthermore, it shows promise for preliminary assessment of interventions with other anti-inflammatory agents, for characterization of the neurochemical profile of the post-laminectomy pain state, and for exploration of newer pharmaceutical agents potentially useful in the prevention or management of the post-laminectomy syndrome. Post-laminectomy scar is but one of many potential causes of the post-laminectomy pain syndrome. Furthermore, a cautionary note must be emphasized as in all studies using preclinical models, conclusions drawn from the studies cannot be extended directly to patients without confirmatory clinical follow-up studies.

Effectiveness of antiadhesion barriers in preventing adhesion after myomectomy in patients with uterine leiomyoma

BACKGROUND

Myomectomy often causes adhesion formation and decreases subsequent fertility. The purpose of the present study was to evaluate the effectiveness of several antiadhesion barrier materials in preventing adhesion after myomectomy.

METHODS

We prospectively classified 63 women undergoing myomectomy alone into four groups according to the type of antiadhesion material used: Hyaluronic acid-carboxymethylcellulose film (Seprafilm) (n = 21, Group 1), Dextran 40 (10% Dextran 40 Low Injection) (n = 17, Group 2), factor 13 with fibrinogen (Beriplast) (n = 12, Group 3) and control (n = 13, Group 4). We performed early second-look laparoscopy after the seventh post-operative day in all patients and examined adhesion formation in the abdominal cavity. The incidence of adnexal adhesions was evaluated according to the American Fertility Association (AFS) adhesion score.

RESULTS

The incidence of uterine adhesion was 14.3% in Group 1, 70.6% in Group 2, 75.0% in Group 3 and 76.9% in Group 4. Adhesion formation in Group 1 was significantly less than that in Group 2 (p = 0.0004), Group 3 (p = 0.0005) and Group 4 (p = 0.0003). The incidence of peritoneal adhesion was 14.3% in Group 1, 29.4% in Group 2, 41.6% in Group 3 and 69.2% in Group 4. Adhesion formation in Group 1 was significantly less than that in Group 4 (p = 0.001). AFS scores in Groups 1-4 were 0.38+/-1.02, 4.58 +/- 7.02, 0.83 +/- 1.99 and 8.53 +/- 8.79 (mean +/- S.D.), respectively. Group 1 had the lowest AFS score and the difference between Group 1 and Group 4 was significant (p < 0.0001). The AFS score in Group 3 was also significantly less than that of Group 4 (p = 0.0009).

CONCLUSION

Seprafilm was highly effective and was superior to the other antiadhesion materials tested in preventing uterine adhesions after myomectomy.

Icodextrin reduces postoperative adhesion formation in rats without affecting peritoneal metastasis

BACKGROUND

Peroperative peritoneal trauma activates a cascade of peritoneal defense mechanisms responsible for postoperative adhesion formation. The same cascade seems to play a role in the process of intra-abdominal tumor recurrence. Icodextrin is a glucose polymer solution that is absorbed slowly from the peritoneal cavity, allowing prolonged "hydroflotation" of the viscera, thereby decreasing adhesion formation. This study evaluated the adhesion-preventing properties of icodextrin and its effect on peritoneal metastasis.

METHODS

Reproducible rat models of peritoneal trauma were used, allowing semiquantitative scoring of adhesion formation or tumor load. In one experiment, peritoneal trauma was inflicted; one group was treated by peroperative intra-abdominal instillation of 7.5% icodextrin, one by instillation of RPMI (placebo), and one had no instillate (controls). In another experiment involving a different model of peritoneal trauma, the coloncarcinoma cell line CC531 was injected intraperitoneally to induce tumor load, again using these three groups.

RESULTS

Treatment of peritoneally traumatized rats with icodextrin caused a 51% reduction in postoperative adhesion formation ( P < .001). However, peroperative intra-abdominal treatment with icodextrin did not affect intraperitoneal tumor cell adhesion and growth of free intra-abdominal tumor cells in rats with this model of severe peritoneal trauma.

CONCLUSION

A 7.5% icodextrin solution is effective in reducing postoperative adhesions without promoting tumor recurrence and therefore may prove useful and safe in oncologic surgery.

Expression of transforming growth factor-beta and extracellular matrix by human peritoneal mesothelial cells and by fibroblasts from normal peritoneum and adhesions: effect of Tisseel

We have previously shown that fibroblasts obtained from adhesions produce greater amounts of transforming growth factor-beta 1 (TGF-beta1) and extracellular matrix (ECM) molecules than normal fibroblasts isolated from normal peritoneum. The purpose of the current studies was to examine the effect of Tisseel (Baxter Healthcare Corporation, Glendale, CA), a fibrin sealant containing fibrinogen, aprotinin (a protease inhibitor), thrombin, and CaC1(2), on TGF-beta1 and ECM production by human peritoneal mesothelial cells, normal peritoneal fibroblasts, and adhesion fibroblasts. Multiplex reverse transcription-polymerase chain reaction using beta-actin as a housekeeping gene was used to determine mRNA levels of TGF-beta1 and ECM in these cells at 6, 12, 24, and 48 hours under normoxic conditions in the following treatment groups : fibrin sealant (Tisseel) alone; fibrin sealant with the two components diluted 1 : 2; fibrin sealant with the sealer protein component reconstituted without aprotinin (a protease inhibitor); fibrin sealant with the sealer protein component reconstituted without aprotinin (and both components diluted 1 : 2); fibrin sealant components diluted to physiologic concentrations; and control (culture media). The test compositions had little effect on TGF-beta1 mRNA expression in mesothelial cells and normal peritoneal fibroblasts, but resulted in a marked reduction of TGF-beta1 from adhesion fibroblasts. Expression of type I collagen by human peritoneal mesothelial cells was not detected; the compositions reduced type I collagen mRNA expression by both types of fibroblasts. Type III collagen was detected at six hours, and increased approximately 50 percent by culturing for 48 hours. Tisseel at full strength and with both components diluted 1 : 2 initially increased type III collagen mRNA levels; in contrast, type III collagen mRNA levels were reduced in mesothelial cells by the fibrin sealant without aprotinin at both concentrations and at physiologic concentrations. In both types of fibroblasts, the Tisseel compositions reduced type III collagen mRNA expression. Fibronectin mRNA were transiently reduced at six hours by approximately 50 percent in the presence of the Tisseel components, but then returned to control levels. Fibronectin mRNA levels were not altered in normal peritoneal fibroblasts, but were reduced by all but the physiologic concentration in adhesion fibroblasts. Tisseel may modulate human peritoneal mesothelial cell, normal peritoneal fibroblast, and adhesion fibroblast function. These results suggest that fibrin sealant prepared from the Tisseel kit without aprotinin has the ability to reduce ECM and TGF-beta1 mRNA levels, especially from adhesion fibroblasts, which may indicate a role in reduction of postoperative adhesion development.

Preventing intra-abdominal adhesions with polylactic acid film: an animal study

PURPOSE

The aim of this study was to evaluate the efficacy of an absorbable polylactic acid film (SurgiWrap) in preventing postoperative intra-abdominal adhesions in an animal model.

METHODS

Forty-four female Sprague-Dawley rats underwent laparotomy with subsequent cecal wall abrasion and abdominal wall injury. Rats were divided equally between untreated and treated groups. Treated rats had a polylactic acid film (SurgiWrap) placed between the cecal and abdominal wall defects. Rats in the untreated group received no barrier material. The animals were killed on postoperative day 21. Two blinded observers, using predetermined criteria, graded the cecum-to-abdominal wall adhesions and estimated the percent of cecal surface area involved in the adhesion. The adhesions were classified as absent, moderate, or severe.

RESULTS

Four rats died postoperatively. Of surviving rats, all of the rats in the untreated group had cecum-to-abdominal wall adhesions, whereas 42.1 percent of rats in the treated group had no adhesions between the cecum and the abdominal wall (two-tailed, P = 0.001). Altogether, 28.6 percent and 71.4 percent of untreated rats experienced moderate and severe adhesions, respectively, compared to 47.4 percent and 10.5 percent of treated rats (two-tailed, P < 0.001).

CONCLUSIONS

Strategic placement of polylactic acid film during abdominal surgery is associated with a significantly reduced rate and severity of postoperative intra-abdominal adhesions in this model. A technique for film placement is suggested.

Seprafilm superior to Gore-Tex in the prevention of peridural fibrosis

OBJECT

This is an investigation into the effects of two barrier membranes in the prevention of peridural fibrosis in an animal model.

METHODS

Seprafilm or Gore-Tex was applied to a laminectomy defect overlying the dura mater in rats separated into treatment groups. A third group of rats underwent laminectomy only and served as controls. Two months postoperatively a histological study was performed to compare the amount of scar tissue in each group. The gross dissection demonstrated that both membranes created a controlled dissection plane, facilitated access to the epidural space, and provided a reduction in the amount of tissue adhering to the dura mater. Statistically, Seprafilm was superior to Gore-Tex in preventing peridural fibrosis (p < 0.05).

CONCLUSIONS

Seprafilm can prevent peridural fibrosis better than Gore-Tex and can be used in humans in spinal surgery.

Efficacy Of Anti-Adhesive Barriers in Secondary Thyroidectomy: An Experimental Study

HYPOTHESIS

This study was conducted to compare the effectiveness of two anti-adhesive barriers (Seprafilm and Interceed) for reducing adhesions after thyroidectomy in a rat model. The anti-adhesive barriers are suggested for use in repeated surgeries in general and the gynecologic fields in particular.

STUDY DESIGN

Controlled, randomized study.

METHODS

Twenty-eight male Wistar Albino rats that underwent right subtotal thyroidectomy were randomly assigned to three groups. One group received Seprafilm (n = 10), and the other received Interceed (n = 10) as anti-adhesive barriers. The third group was the control group (n = 8). At postoperative day 14, the rats were killed under general anesthesia, and the surgical fields were evaluated for the adhesion formation. The extent of the adhesion formation is scored from 0 (no adhesions) to 2 (fibrous adhesions that required sharp dissection). Histopathologically, chronic inflammation, histiocyte, fibroblast, fibrosis, collagen, vascularization, granuloma, giant cell, and fat necrosis were examined.

RESULTS

All the subjects in the control group, 7 of 10 in the Interceed group, and 4 of 10 in the Seprafilm group needed to be dissected bluntly or sharply. There was significant difference between the Seprafilm and the control group (P < .05) whereas there was no significant difference between the Interceed group and the control group (P > .05). When examined histopathologically, the criteria showing adhesion, such as fibrosis, fibroblast, and collagen were higher in the control group compared with the Seprafilm and Interceed groups. There was no significant difference between the Seprafilm and Interceed groups, whereas a significant difference was found between these two groups and the control group.

CONCLUSION

This study suggests that both Seprafilm and Interceed decrease the incidence of posthyroidectomy adhesions in a rat model. Both agents showed no foreign body reaction.

Effect of Tisseel® on expression of tissue plasminogen activator and plasminogen activator inhibitor-1

OBJECTIVE

To examine the effect of fibrin sealant on mRNA expression of factors regulating plasminogen activator activity in human peritoneal cells. Plasminogen activator activity is thought to play a pivotal role in degradation of the proteinaceous mass that develops after surgical procedures. Reduction of plasminogen activator activity, as occurs with tissue trauma, results in increased postoperative adhesion development.

DESIGN

Tissue culture for 6, 12, 24, and 48 hours.

SETTING

University research laboratory.

PATIENTS

Source of mesothelial cells with fibroblasts.

INTERVENTION(S)

Measurement of mRNA expression of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1).

MAIN OUTCOME MEASURE(S)

Multiplex reverse transcriptase/polymerase chain reaction (RT/PCR) was used to determine relative change in t-PA and PAI-1 mRNA levels under six conditions: [1]. fibrin sealant (Tisseel); [2]. fibrin sealant (Tisseel) two components diluted 1:2; [3]. fibrin sealant (Tisseel) sealer protein component reconstituted without aprotinin (a protease inhibitor); [4]. fibrin sealant (Tisseel) sealer protein component reconstituted without aprotinin, both components diluted 1:2; [5]. fibrin sealant (Tisseel) components diluted to physiologic concentrations; and [6] control (culture media).

RESULTS

The mRNA levels of t-PA and PAI-1 by human peritoneal cells were unchanged during 48 hours. In mesothelial cells, the addition of the compositions increased t-PA mRNA levels. A selective increase was observed in the normal peritoneal fibroblasts at the later time points; similar increases were identified in adhesion fibroblast cultures. In mesothelial cells, the more concentrated compositions generally increased PAI-1 mRNA above control levels, whereas in normal peritoneal fibroblasts PAI-1 levels generally remained unchanged. In contrast, in adhesion fibroblasts, PAI-1 levels decreased over time with treatment.

CONCLUSION(S)

Fibrin sealant, in the presence and absence of aprotinin, increases both t-PA and PAI-1 expression by human peritoneal cells; changes not seen with physiologic concentrations of fibrin sealant. These observations suggest that in addition to its ability to help achieve hemostasis, fibrin sealant affects the healing process by altering components of the plasminogen activator system, which may be of benefit in the reduction of postoperative adhesions.

Prevention of adhesions to polypropylene mesh

BACKGROUND

Polypropylene mesh used to repair abdominal wall hernias routinely induces dense adhesions if there is direct contact between the mesh and the viscera. Adhesions may lead later to difficult reoperation, intestinal obstruction, or enteric fistula.

STUDY DESIGN

A 2.5-cm square defect was surgically created in the rat abdominal wall and replaced with: 1) polypropylene mesh, 2) Sepramesh (SM), or 3) SM plus Seprafilm. Each group included 20 animals. Adhesion area as a percent of the mesh surface was subjectively quantitated by means of laparoscopy and at sacrifice. Evaluations varied from 7 to 28 days after mesh placement. Tissues were harvested at intervals for scanning electron microscopy.

RESULTS

Adhesions were complete by day 7, with no change in area thereafter. Adhesion-free mesh surfaces were found on scanning electron microscopy to be carpeted with mesothelial cells from day 5 on. Polypropylene mesh alone induced adhesions in all rats (20/20). The mean area involved was 92%. With SM, 9 of 20 were adhesion-free. The mean area was 15%. When Seprafilm was added to SM, minimal adhesions developed in 5 of 20 rats, the mean area being 2%. Four of the five were single point omental attachments.

CONCLUSIONS

1) Sepramesh alone reduces polypropylene mesh adhesions by roughly three-quarters. 2) Sepramesh plus Seprafilm nearly eliminates such visceral adhesions. 3) Mesothelial cell coverage of polypropylene mesh confers adhesion resistance.

Evaluation of a bioabsorable polylactide film in a large animal model for the reduction of retrosternal adhesions

OBJECTIVES

An adult pig model of retrosternal adhesion formation via an inferior hemisternotomy was used to evaluate the formation and development of pericardial and retrosternal adhesions, as well as adhesion reduction using two thicknesses of a bioabsorbable polylactide film.

MATERIALS AND METHODS

Twenty-five adult female pigs (70 kg) were allocated to either a control group or four different treatments using two thicknesses (0.02 or 0.05 mm) of a polylactide film. In each animal, the film was placed either inside the pericardium or inside and outside the pericardium.

RESULTS

All animals demonstrated adhesions between the posterior and lateral surfaces of the heart and pericardium. Thick fibrous retrosternal adhesions and pericardial adhesions were noted in the control animals with complete obliteration of the anatomical plane. The polylactide films preserved the anatomical planes and reduced the adhesion response.

CONCLUSIONS

A reproducible animal model was used to examine the formation and reduction of retrosternal and pericardial adhesions. A polylactide film placed inside the pericardium or between the heart and sternum was able to limit adhesion formation and maintain the anatomical planes, which would facilitate reentry.

Application of Adcon-P or Seprafilm in consecutive laparotomies using a murine model

BACKGROUND

Intraabdominal administration of antiadhesive products may reduce postoperative adhesions. We compared two barriers, Adcon-P (Gliatech, Cleveland, Ohio) and Seprafilm (Genzyme, Cambridge, Massachusetts), in a relaparotomy murine model to evaluate whether using them during the first and second laparotomy reduces adhesion formation better than using them only during the relaparotomy.

METHODS

One-hundred and fifty mice underwent cecal abrasion, followed by complete adhesiolysis and cecal abrasion 21 days later. All were sacrified 21 days after the second operation. The mice (30 to a group) received Adcon-P in both surgeries (AA), Seprafilm in both surgeries (SS), Adcon-P in the second surgery (CA), Seprafilm in the second surgery (CS), or neither barrier (CC). Difficulty of adhesiolysis was blindly assessed with a 6-point scoring system and sites of adhesions were determined with a yes/no questionnaire.

RESULTS

The AA group had lower adhesiolysis score than SS, CS, and CC groups, and had fewer adhesions over cecum and between cecum and intra-peritoneal fat than all other groups. The numbers of the animals had adhesions between the cecum and abdominal wall were similar between the treatment groups. No difference was observed between SS and CS groups in any analysis.

CONCLUSIONS

Using Adcon-P starting with the first laparotomy more effectively reduce adhesion formation and difficulty of adhesiolysis. Using Seprafilm only in the relaparotomy is as effective as using it in both laparotomies. Adcon-P is more effective in preventing adhesions to different sites than Seprafilm except to the abdominal wall under the midline incision.

Prevention and treatment of gastrointestinal adhesions

As with many aspects of clinical medicine, there is yet to be a single or definitive cure for postoperative adhesion formation. Current methods of prevention target risk factors predisposing horses to adhesion formation. Systemic pharmacologic therapies, such as antimicrobials, nonsteroidal anti-inflammatory drugs, Salmonella antiserum, and hyperimmune plasma, help to reduce abdominal inflammation and minimize the effects of endotoxemia. Intra-abdominal or systemic heparin aids in enhancing peritoneal fibrinolysis. Prokinetic therapy promotes early postoperative return of intestinal motility, minimizing the propensity for adhesion formation between apposing adynamic segments of intestine. Mechanical separation of potentially adhesiogenic serosal and peritoneal surfaces is commonly achieved with use of abdominal lavage, protective coating solutions, and barrier membranes. Ongoing and future research is directed toward a better understanding of the local effects of intestinal trauma and the corresponding response of the fibrinolytic system. Recognition of horses at high risk for adhesion formation helps to guide the equine surgeon to an appropriate perioperative and intraoperative plan for adhesion prevention, including good surgical technique and a combination of adjunct therapies.

Seprafilm (modified hyaluronic acid and carboxymethylcellulose) acts as a physical barrier

OBJECTIVE

To characterize the molecular changes that occur in normal fibroblasts, adhesion fibroblasts, and mesothelial cells as a result of exposure to modified hyaluronic acid and carboxymethylcellulose (Seprafilm).

SETTING

University research laboratory.

DESIGN

Human mesothelial and fibroblast cell culture.

MAIN OUTCOME MEASURE(S)

Multiplex reverse transcriptase polymerase chain reaction was used to examine control and Seprafilm-treated normal peritoneal fibroblasts, adhesion fibroblasts, and mesothelial cells in culture for levels of messenger RNA from molecules known to be associated with adhesion development (transforming growth factor-beta 1, type I collagen, matrix metalloproteinase-1, matrix metalloproteinase-2, tissue inhibitor of metalloproteinase-1, and tissue plasminogen activator).

RESULT(S)

Seprafilm treatment of normal peritoneal fibroblasts, adhesion fibroblasts and mesothelial cells did not alter the expression of markers examined.

CONCLUSION(S)

In the absence of a biological effect of Seprafilm on markers known to be involved in postoperative adhesion development, the ability of Seprafilm to reduce postoperative adhesions is most likely caused by its effect as a physical barrier.

Pathophysiology of intra-abdominal adhesion and abscess formation, and the effect of hyaluronan

BACKGROUND

Intra-abdominal adhesions and abscesses cause significant morbidity and mortality. The formation of fibrin in the abdominal cavity is a common pathophysiological pathway for both. The aim of this review was to investigate the pathophysiology of intra-abdominal adhesions and abscesses, and to explore the possible sites of action of hyaluronan.

METHODS

Data were reviewed from the literature using the Medline database.

RESULTS

Both surgery and peritonitis disturb the equilibrium between coagulation and fibrinolysis in the abdominal cavity in favour of the coagulation system. Hyaluronan-based agents reduce adhesion formation after surgery. Moreover, hyaluronan solution reduces abscess formation in experimental peritonitis. Possible mechanisms of action include mechanical separation of wound surfaces, improvement of peritoneal healing, modulation of the inflammatory response and enhanced fibrinolysis.

CONCLUSION

Diminished fibrin degradation is a common pathway for the formation of adhesions and abscesses. The potential of hyaluronan-based agents to reduce intra-abdominal adhesions and abscesses in abdominal surgery and sepsis is a promising new concept. Elucidating the mechanisms involved and the clinical application of hyaluronan in peritonitis are challenges for future research.

Histological effects of fibrin glue on nervous tissue: a safety study in rats

BACKGROUND

Little is known of the histologic effects of fibrin glue on normal nervous tissue. To verify the safety of intracranial application of fibrin glue, we investigated the histologic effects of fibrin glue on brain tissue and intracranial nerves of rats.

METHODS

In Group I (n = 12), bifrontal craniotomy with opening of the dura and arachnoid was performed, and on one side one droplet of fibrin glue was applied into the subarachnoid space. In Group II (n = 12), a unilateral temporal craniotomy was performed, the cavernous sinus was opened, and one drop of fibrin glue was applied to the trigeminal nerve. The controls for Group II (n = 8) were operated in the same way but without application of the fibrin glue. Rats were sacrificed at 1, 3, 7, and 28 days after surgery. The brains and nerves were processed for histologic examination and were semi-quantitatively scored for neuronal damage, gliosis, edema, fibroplasia, inflammatory reaction, axonal damage, and myelin damage.

RESULTS

No differences were found in the occurrence of neuronal damage, gliosis, edema, fibroplasia, axonal damage, or myelin damage between rats with and without fibrin glue application. In Group I the inflammatory reaction seen at Day 7 was more severe on the fibrin glue side when compared to the control side. At Day 28, however, this difference had resolved.

CONCLUSIONS

In this morphological safety study, intracranial application of fibrin glue in a rat model does not induce extra brain damage, intracranial nerve damage, or scar tissue formation.

Temporary ovarian suspension at laparoscopy for prevention of adhesions

We performed an innovative technique of temporary ovarian suspension after operative laparoscopy for stage 3 and 4 endometriosis and evaluated the results in a retrospective study. Subjects were 20 women who underwent operative laparoscopy for infertility. Temporary ovarian suspension to the anterior abdominal wall was performed as the last step in the surgical procedure. It was done in an attempt to separate adhesiogenic surfaces during the initial phase of tissue healing (5-7 days). No complications occurred. After excluding patients who had additional infertility factors and/or were of advanced reproductive age, nine women tried to conceive spontaneously. Of these, five conceived (55%): three delivered, one pregnancy continues (80%), and one woman had an ectopic pregnancy (20%). Of the remaining 15 patients who failed to conceive spontaneously, 5 had a second-look laparoscopy. In four patients (80%), we found no evidence of recurrent adhesions. The remaining 20% had minimal adhesions. Temporary ovarian suspension appears to be simple and safe, and may be effective in preventing postoperative adhesions near the ovaries after operative laparoscopy for advanced endometriosis.