Prevention of peritoneal adhesions by a new povidone-iodine/PVP solution

Advancement of Biomaterial-Based Postoperative Adhesion Barriers

Postoperative peritoneal adhesion (PPA) is a prevalent incidence that generally happens during the healing process of traumatized tissues. It causes multiple severe complications such as intestinal obstruction, chronic abdominal pain, and female infertility. To prevent PPA, several antiadhesion materials and drug delivery systems composed of biomaterials are used clinically, and clinical antiadhesive is one of the important applications nowadays. In addition to several commercially available materials, like film, spray, injectable hydrogel, powder, or solution type have been energetically studied based on natural and synthetic biomaterials such as alginate, hyaluronan, cellulose, starch, chondroitin sulfate, polyethylene glycol, polylactic acid, etc. Moreover, many kinds of animal adhesion models, such as cecum abrasion models and unitary horn models, are developed to evaluate new materials' efficacy. A new animal adhesion model based on hepatectomy and conventional animal adhesion models is recently developed and a new adhesion barrier by this new model is also developed. In summary, many kinds of materials and animal models are studied; thus, it is quite important to overview this field's current progress. Here, PPA is reviewed in terms of the species of biomaterials and animal models and several problems to be solved to develop better antiadhesion materials in the future are discussed.

Prevention of adhesions by bioresorbable tissue barrier following laparoscopic intraabdominal mesh insertion

Intraabdominal adhesions represent a significant problem because of the morbidity associated with adhesive disease, including small bowel obstruction, difficulties in reoperative surgery, and possibly chronic pain. Coating solution of sodium hyaluronate (Sepracoat; Genzyme Production-Surgical Products, Cambridge, MA) was studied in New Zealand white rabbits to determine its potential role for prevention of postoperative adhesions following laparoscopic intraabdominal mesh insertion. A 2-cm polypropylene mesh was inserted laparoscopically to the left iliac fossa and fixed to anterior abdominal wall using a single prolen suture. Group 1 (n = 10) acted as the control group. Mesh was coated using 4% sodium hyaluronate in phosphate buffered saline (Sepracoat) in Group 2 (n = 10). Fourteen days later, all animals underwent diagnostic laparoscopy, and findings were recorded. All animals then were killed, the abdominal cavities were inspected, and adhesions were graded from 0 to 4. All meshes were removed and sent for histologic examination. The degrees of inflammation, fibrosis, and congestion were scored. No adhesions were seen on trocar sites on both groups. Eight of 10 animals in the control group and 5 of 10 animals in the study group had intraabdominal adhesions. The scoring of adhesions revealed that study group had only one (10%) significant adhesion, whereas the control group had eight (80%; < 0.001). Our study suggests that the Sepracoat reduces the incidence and severity of abdominal adhesions following laparoscopic mesh insertion and should be considered as a prophylactic agent, especially in those undergoing laparoscopic transabdominal mesh repair for hernia.

Halofuginone--an inhibitor of collagen type I synthesis--prevents postoperative formation of abdominal adhesions

OBJECTIVE

To evaluate the effects of halofuginone, a specific inhibitor of collagen type I synthesis, on the postoperative formation of abdominal adhesions in rats.

SUMMARY BACKGROUND DATA

Postoperative adhesions remain the leading cause of small bowel obstruction in the Western world. Surgical trauma causes the release of a serosanguineous exudate that forms a fibrinous bridge between two organs. This becomes ingrown with fibroblasts, and subsequent collagen deposition leads to the formation of a permanent adhesion. Most of the drugs used have been clinically ineffective, and none has been specific to a particular extracellular matrix molecule. Therefore, there are serious concerns about the toxic consequences of interfering with the biosynthesis of other collagens, other matrix proteins, or vital collagen-like molecules.

METHODS

Adhesions were induced by scraping the cecum until capillary bleeding occurred. The adhesions were scored 21 days later. Halofuginone was either injected intraperitoneally (1 microg/25 g body weight) every day, starting on the day of operation, or added orally at concentrations of 5 or 10 mg/kg, starting 4 days before the operation. Collagen alpha1(I) gene expression was evaluated by in situ hybridization, total collagen was estimated by Sirius red staining, and collagen type III was detected by immunohistochemistry.

RESULTS

The adhesions formed between the intestinal walls were composed of collagen and were populated with cells expressing the collagen alpha1(I) gene. Regardless of the administration procedure, halofuginone significantly reduced the number and severity of the adhesions. Halofuginone prevented the increase in collagen alpha1(I) gene expression observed in the operated rats, thus reducing collagen content to the control level. In fibroblasts derived from abdominal adhesions, halofuginone induced dose-dependent inhibition of collagen alpha1(I) gene expression and collagen synthesis. Collagen type III levels were not altered by adhesion induction or by halofuginone treatment.

CONCLUSIONS

Upregulation of collagen synthesis appears to have a critical role in the pathophysiology of postoperative adhesions. Halofuginone, an inhibitor of collagen type I synthesis, could be used as an important tool in understanding the role of collagen in adhesion formation, and it may become a novel and promising antifibrotic agent for preventing postoperative adhesion formation.

Prevention of intestinal adhesions after laparotomy in a rat model--a randomized prospective study

We prospectively studied the effect of a foam composite containing glycerin, propylene glycol, polyol, stearine, stearate and silicone oil, which is known to form a temporary barrier layer when applied to epithelial surface, on adhesion prevention in rats. The small intestine abrasion model was used for creation of adhesions. Sixty male Sabra rats of a mean weight of 295 +/- 23 g were randomly assigned into four groups: group 1 (n = 20) underwent laparotomy and abrasion; group 2 (n = 20) underwent laparotomy, abrasion and intraperitoneal instillation of the foam composite; group 3 (n = 10) underwent laparotomy with abrasion and a second laparotomy with adhesiolysis 2 weeks later; and group 4 (n = 10), was treated in the same way as group 3 but during the second laparotomy the foam composite was instilled intraperitoneally. All animals were relaparotomized 2 weeks (groups 1 and 2) and 4 weeks (groups 3 and 4) after the initial laparotomy for adhesion scoring performed by a blinded independent investigator using the standard 0-3 adhesion grading score. Representative specimens of small intestine and liver from animals in groups 2 and 4 were analyzed. A significantly lower mean adhesion score was noted in group 2 (1.15 +/- 0.3) compared with that of group 1 (2.65 +/- 0.1) or group 3 (2.60 +/- 0.1) (P < 0.01). Group 4 had a significantly lower score (1.4 +/- 0.3) than group 3 or group 1 (P < 0.05). There was no significant difference in the mean adhesion score between groups 1 and 3. Histological examination revealed no evidence of residual foam composite or adverse reaction to its use in the intestine and liver. The foam composite tested may reduce the severity of intestinal adhesions after laparotomy and may also reduce the severity of recurrent adhesions after adhesiolysis. Intraperitoneal use of this composite is safe in rats. The exact mechanism of action is unclear but may be related to the formation of a temporary microlayer that coats the injured surface of the intestine and facilitates healing without adhesion formation. Further investigation is needed to evaluate its full potential.

Sclerosing encapsulating peritonitis after intraperitoneal use of povidone iodine

BACKGROUND

The use of intraperitoneal povidone iodine as an agent for peritoneal lavage in colorectal surgery is controversial. Although it possesses a wide range of antimicrobial activity and is rapidly lethal to dissociated colorectal cancer cells in vitro, concern about its potential toxicity remains.

METHODS

Two cases of sclerosing encapsulating peritonitis (SEP) following elective colorectal surgery are presented. In each case the peritoneal cavity was lavaged with an aqueous povidone iodine solution. The surgical literature on the intraperitoneal use of povidone iodine is reviewed.

RESULTS

Significant morbidity resulted from the postoperative development of SEP in both of our patients. In one patient an ileo-anal pouch could not be fashioned following an initial colectomy, and in the second patient a small-bowel obstruction required a laparotomy and a period of intravenous nutrition before an oral diet could be tolerated.

CONCLUSION

The use of povidone iodine for peritoneal lavage in colorectal surgery is to be cautioned against in concentrations of > 1%.

Effect of phosphatidylcholine on postoperative adhesions after small bowel anastomosis in the rat

The possibility of preventing postoperative adhesions using phosphatidylcholine (PC) was studied in rats. A small bowel anastomosis was created using continuous or interrupted 5/0 silk sutures. Adhesions were measured by recording the maximal length of adhesions around the anastomosis and the number of organs involved in the adhesions. PC was administered intraperitoneally either as a single dose or as three separate doses. Postoperative adhesions developed in all animals; the degree of adhesion was independent of the suture technique used. PC given once at a dose of 20 mg significantly decreased adhesion formation (P less than 0.01). The mechanism underlying this effect may be that the exogenous PC provides a lubricant layer replacing endogenous hydrolysed phospholipid. The result with repeated PC administration was not different from that after a single dose. Increasing the single dose of PC to 40 or 60 mg resulted in anastomotic dehiscence and subsequent peritonitis. It is concluded that PC in a single dose of 20 mg reduces adhesion formation after small bowel anastomosis in the rat.

Phosphatidylcholine prevents postoperative peritoneal adhesions: an experimental study in the rat

Phosphatidylcholine (PC) is the main constituent of the surface-active material coating peritoneal mesothelium. It may prevent postoperative adhesion formation through production of a lubricant film on mesothelial defects. We therefore examined the effect of its soluble form on surgically induced intraabdominal adhesions in rats. The adhesions were induced at laparotomy by any of four different operative models. PC was administered intraperitoneally (20 mg/rat) or intravenously (20 mg/rat or 50 mg/rat) at the end of the operation and on the second and third postoperative day. It was found that the degree of postoperative adhesion formation was significantly reduced by the intraperitoneal injection of PC in all 4 models. In contrast, no effect was achieved by the intravenous injection of PC, not even at a very high dose level. Our results suggest that soluble PC administered intraperitoneally might be a potent adjunct in postoperative adhesion prevention.

Reoperation for small intestinal obstruction

Today, intestinal adhesions represent the most frequent etiology for complete or partial intestinal obstruction. Although partial obstruction can be treated nonoperatively with a considerable likelihood of success, intestinal strangulation cannot uniformly be predicted or prevented. Complete intestinal obstruction is associated with a significant incidence of strangulation if not treated by a vigorous surgical approach. Consequently, complete intestinal obstruction secondary to adhesions is still a surgical disease. Attempts at control of the adhesion process include mechanical methods to prevent subsequent obstruction and chemical methods to prevent the adhesion process itself. The invasive mechanical methods appear dated. A variety of agents have been used either systemically or in the peritoneal cavity to prevent the establishment of intra-abdominal adhesions. Agents that do not contribute to subsequent morbidity or impede the native host defense mechanisms should be utilized. High-molecular-weight dextran and nonsteroidal anti-inflammatory agents show some promise of being both safe and effective. As is frequently the case, the bottom line in preventing and treating intra-abdominal adhesions is appropriate surgical technique. Intestinal adhesions can be related clearly to leaving damaged, devitalized, or ischemic tissue in the peritoneal cavity or to excessive roughness in handling of tissues. Steps such as avoidance of excessive suture material and unnecessary handling of the bowel will do much to prevent subsequent adhesion generation. Likewise, the surgical lysis of intraperitoneal adhesions is frequently fraught with complications such as intra-abdominal abscess or postoperative incisional failure. This is again related to surgical technique and most directly to the use of blunt dissection to divide adhesions. Knife dissection in the lysis of adhesions is recommended. This technique, combined with excellent intraoperative hemostasis, can be associated with a marked diminution in the incidence of postoperative fistulas and abscesses.

Prevention of intraperitoneal adhesions: a comparison of noxythiolin and a new povidone-iodine/PVP solution

Peritoneal adhesions were induced in 250 female Wistar rats by the excision and closure of a right lower quadrant parietal peritoneal defect. After closure of the defect each rat was randomly allocated to one of five treatment groups: A, control with no instillate; B, control with Ringer solution; C, noxythiolin 0.5 per cent solution; D, noxythiolin 1 per cent solution; E povidone-iodine/PVP solution. Two millilitres of the appropriate solution were injected into the peritoneal cavity just before closure of a standard 4-cm midline incision. Assessment of adhesion formation was made at 1 week in ignorance of the treatment group. Noxythiolin 1 per cent was more effective than Ringer solution and noxythiolin 0.5 per cent in reducing the mean number of adhesions (P less than 0.05) but was inferior to povidone-iodine/PVP (P less than 0.05). Povidone-iodine/PVP solution significantly reduced the number of adhesions compared with the four other groups. In addition, it significantly reduced the mean length of attachment of each adhesion compared with the two control groups (P less than 0.001).