Orally delivered antibiotics which lower bacterial numbers decrease experimental intra-abdominal adhesions

Postoperative Abdominal Adhesions: Clinical Significance and Advances in Prevention and Management

Postoperative adhesions remain one of the more challenging issues in surgical practice. Although peritoneal adhesions occur after every abdominal operation, the density, time interval to develop symptoms, and clinical presentation are highly variable with no predictable patterns. Numerous studies have investigated the pathophysiology of postoperative adhesions both in vitro and in vivo. Factors such as type and location of adhesions, as well as timing and recurrence of adhesive obstruction remain unpredictable and poorly understood. Although the majority of postoperative adhesions are clinically silent, the consequences of adhesion formation can represent a lifelong problem including chronic abdominal pain, recurrent intestinal obstruction requiring multiple hospitalizations, and infertility. Moreover, adhesive disease can become a chronic medical condition with significant morbidity and no effective therapy. Despite recent advances in surgical techniques, there is no reliable strategy to manage postoperative adhesions. We herein review the pathophysiology and clinical significance of postoperative adhesions while highlighting current techniques of prevention and treatment.

Fucoidan film safely inhibits surgical adhesions in a rat model

BACKGROUND

The purpose of this study was to evaluate the in vivo efficacy of 13 compounds and to further characterize the load limiting and potential toxicity of the most efficacious compound. The cascade of biochemical and molecular events that results in the formation of postsurgical adhesions provides numerous theoretical opportunities for prophylactic intervention.

METHODS

Candidate agents were loaded into sodium hyaluronate (HA) films and administered to male Sprague-Dawley rats using a cecal-sidewall model of surgical adhesions. An adhesion score was obtained for each rat based on the strength and extent of the adhesions. The most efficacious agent, fucoidan, was further evaluated in a load-limiting study with a concentration range of 0.0033 to 33% w/w per film. The potential toxicity of fucoidan was evaluated in a separate study by comparison of hematology findings, blood chemistry, urinalysis, and incision thickness from rats administered control films or 33% w/w fucoidan films 1 to 4 d prior to sacrifice.

RESULTS

Fucoidan loaded films reduced adhesion scores by approximately 90% compared with control films (P<0.05). A total of 50% to 100% of animals were adhesion free at fucoidan film loadings of 0.33% to 33% w/w compared with all control film animals having adhesions. No adverse effects were observed from 33% w/w fucoidan films equivalent to approximately 30 mg fucoidan/kg body weight.

CONCLUSIONS

Local administration of fucoidan film during rat cecal-sidewall surgery safely reduced adhesion scores by approximately 90% and resulted in 50% to 100% of animals being adhesion free.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

Enteric bacteria and their antigens may stimulate postoperative peritoneal adhesion formation

BACKGROUND

Intraabdominal sepsis causes exuberant inflammation, which results in dense adhesions. Translocation of enteric bacteria and/or their antigens after laparotomy may therefore also affect peritoneal healing by promoting local release of proinflammatory cytokines. Our hypothesis was that targeted counter therapy could be beneficial if such contamination was to augment postoperative adhesion formation.

METHODS

Two endotoxin-hyposensitive mouse strains (C3H/HeJ and C57BL/10ScCr) and their syngeneic counterparts (C3H/HeN and C57BL10/ScSn, respectively) underwent reproducible adhesion-inducing operation (AIO) (n=10/group) with sacrifice and blinded adhesion grading 14 days later. In addition, CD-1 mice were gavaged with fluorescein isothiocyanate labeled-lipopolysaccharide (FITC-LPS) prior to either AIO or sham laparotomy and had both peritoneal macrophages and circulating monocytes assessed by flow cytometry afterward. The cytokine-release response of resident peritoneal cells to LPS stimulation was assessed in vitro (murine peritoneal mast cell cultures) and in vivo (unoperated CD-1 mice administered LPS intraperitoneally [10 & 50 microg/mouse]). Finally, CD-1 mice (n=10/group) had AIO and received either bactericidal/permeability increasing protein (rBPI, 2 mg/mouse) or vehicle solution in the early postoperative period with assessment of adhesion formation 2 weeks later.

RESULTS

Both HeJ and ScCr mice had less adhesions than their controls (P=.0015 and .0001, respectively, Mann Whitney U test). FITC-LPS uptake by peritoneal macrophages was striking after AIO. Intraperitoneal LPS provoked significant local vascular endothelial growth factor (VEGF) release as did the process of AIO. In vitro, LPS induced significant interleukin-(IL)-6 release from isolated mast cells. Intraperitoneal administration of rBPI to CD-1 mice early after AIO markedly attenuated subsequent adhesion formation (P=.0003).

CONCLUSIONS

Peritoneal adhesion formation is exacerbated by peritoneal contamination due to translocation after laparotomy and may be attenuated by therapeutic antagonism.

Prevention of postsurgery-induced abdominal adhesions by electrospun bioabsorbable nanofibrous poly(lactide-co-glycolide)-based membranes

OBJECTIVES

The objective of this study was to evaluate the efficacy of nonwoven bioabsorbable nanofibrous membranes of poly(lactideco-glycolide) for prevention of postsurgery-induced abdominal adhesions.

SUMMARY BACKGROUND DATA

Recent reports indicated that current materials used for adhesion prevention have only limited success. Studies on other bioabsorbable materials using a new fabrication technique demonstrated the promising potential of generating an improved and inexpensive product that is suitable for a variety of surgical applications.

METHODS

All rats underwent a midline celiotomy. The cecum was identified and scored using an abrasive pad until serosal bleeding was noted on the anterior surface. A 1 x 1 cm of abdominal wall muscle was excised directly over the cecal wound. The celiotomy was then closed in 2 layers immediately (control) after a barrier was laid in between the cecum and the abdominal wall. All rats underwent a second celiotomy after 28 days to evaluate the extent of abdominal adhesions qualitatively and quantitatively.

RESULTS

Cecal adhesions were reduced from 78% in the control group to 50% in the group using biodegradable poly(lactide-co-glycolide) (PLGA) nonwoven nanofibrous membranes (n = 10, P = 0.2) and to 22% in the group using membranes containing PLGA and poly(ethylene glycol)/poly(D,L-lactide) (PEG-PLA) blends (n = 9, P = 0.03). Electrospinning method also enabled us to load an antibiotic drug Cefoxitin sodium (Mefoxin; Merck Inc., West Point, PA) with high efficacy. The electrospun PLGA/PEG-PLA membranes impregnated with 5 wt% cefoxitin sodium, which amounts to approximately 10% of the systemic daily dose typically taken after surgery in humans, completely prevented cecal adhesions (0%) in rats.

CONCLUSIONS

Electrospun nonwoven bioabsorbable nanofibrous membranes of poly(lactide-co-glycolide) were effective to reduce adhesions at the site of injury using an objective rat model. The membrane acted as a physical barrier but with drug-delivery capability. The combined advantages of composition adjustment, drug-loading capability, and easy placement handling (relatively hydrophobic) make these membranes potentially successful candidates for further clinical evaluations.