Melvin H.Thornton 1, Douglas B.Johns 2,4, Joseph D. Campeau 1, Fred Hoehler 3 and Gere S.DiZerega 1

Transcription

1 Human Reproduction vol.13 no.6 pp , 1998 Clinical evaluation of 0.5% ferric hyaluronate adhesion prevention gel for the reduction of adhesions following peritoneal cavity surgery: open-label pilot study Melvin H.Thornton 1, Douglas B.Johns 2,4, Joseph D. Campeau 1, Fred Hoehler 3 and Gere S.DiZerega 1 1 Livingston Reproductive Biology Laboratory, University of Southern California School of Medicine, 2 Research and Development, Ethicon, Inc. and 3 Statistics and Information Systems Consulting, Santa Ana, CA, USA 4 To whom correspondence should be addressed The objective of this study was to assess the safety and to make a preliminary assessment of the efficacy of 0.5% ferric hyaluronate adhesion prevention gel in reducing adhesions in patients undergoing peritoneal cavity surgery by laparotomy, with a planned second-look laparoscopy. The study was a randomized, open-label, placebo-controlled, parallel-group design in patients desirous of fertility at the Women s and Children s Hospital, Department of Obstetrics and Gynecology, University of Southern California School of Medicine, Los Angeles, California. Female patients aged 24 to 41 years received 300 ml 0.5% ferric hyaluronate adhesion prevention gel or lactated Ringer s solution as an intraperitoneal instillate at the completion of the laparotomy procedure. At second-look laparoscopy 4 12 weeks after the laparotomy, the presence of adhesions was evaluated. Haematology and serum chemistry were determined throughout the study interval. All patients tolerated the procedures well and did not manifest any serious adverse events. At second-look laparoscopy, patients treated with 0.5% ferric hyaluronate adhesion prevention gel had significantly fewer adhesions than control patients. When adhesions did form, they were significantly less extensive and less severe in patients who received 0.5% ferric hyaluronate adhesion prevention gel. In conclusion, 0.5% ferric hyaluronate adhesion prevention gel was safe and highly efficacious in the reduction of the number, severity and extent of adhesions throughout the entire abdomen following peritoneal cavity surgery. Key words: adhesion/adhesion prevention clinical/fertility/ hyaluronate/0.5% ferric hyaluronate adhesion prevention gel Introduction Minimization of peritoneal injury forms the basis of modern surgical and microsurgical techniques and is the most important component in the prevention or reduction of postoperative adhesions. However, despite strict adherence to these principles, serosal trauma inevitably occurs, resulting in adhesion formation. Adhesion formation after peritoneal surgery is a major cause of postoperative bowel obstruction, infertility and chronic pelvic pain (dizerega and Rodgers, 1992; Howard, 1993; Stricker et al., 1994). Therefore, a method by which post-surgical adhesion formation could be reduced or prevented would be of great benefit in reducing postoperative morbidity. Studies have indicated that placement of an absorbable barrier of oxidized regenerated cellulose [Interceed (TC7) Absorbable Adhesion Barrier, Ethicon, Inc., Somerville, NJ, USA], expanded polytetrafluoroethylene (Preclude Surgical Membrane, W.L. Gore & Assoc., Flagstaff, AZ, USA) or hyaluronic acid/carboxymethylcellulose (Seprafilm Bioresorbable Membrane, Genzyme Corp., Cambridge, MA, USA) between injury sites, or addition of a viscous solution (Hyskon 32% Dextran 70, Pharmacia Inc., Piscataway, NJ; Sepracoat Hyaluronic Acid Coating Solution, Genzyme Corp., Cambridge, MA, USA) to the peritoneal cavity during or after surgery can reduce postoperative adhesion formation (Diamond et al., 1996; Thornton and dizerega, 1996). In the case of Interceed, Preclude or Seprafilm, the surgeon must predict potential sites of adhesion formation in order to determine placement site and optimize barrier benefit. A dilute solution of hyaluronic acid, Sepracoat, has only been shown to be effective in reducing the number of de novo adhesions at sites remote from the surgical trauma (Diamond et al., 1996), while reports indicate that Hyskon is ineffective in several types of pelvic surgery because of gravitational pooling in the cul-desac (dizerega, 1994). In addition, the use of Hyskon in clinical practice has shown some undesirable side-effects resulting from the accumulation of intraperitoneal ascites due to oncotic properties (dizerega and Campeau, 1994). Interest therefore continues in the development of an intraperitoneal device that functions more broadly as a post-surgical adhesion prophylactic. Sodium hyaluronate is a naturally occurring high molecular weight mucopolysaccharide comprising sodium D-glucuronate and N-acetyl-D-glucosamine, which are linked as disaccharides by β1-3 linkages. The subunits are joined by β1-4 glycosidic bonds. Sodium hyaluronate is hydrolysed to disaccharide or tetrasaccharide units by the action of the enzyme hyaluronidase. Sodium hyaluronate has been shown to significantly reduce adhesion formation in animal models and is believed to function through a physical effect by providing a viscous, lubricious coating on the peritoneal surfaces (Rodgers et al., 1997). Although recent clinical studies demonstrated safety when sodium hyaluronate was administered as a pre-coat throughout surgery and was left as an instillate, it has only been shown to be effective at reducing the number of de novo adhesions at sites remote from the surgical trauma (Diamond et al., 1996) European Society for Human Reproduction and Embryology

2 Adhesion prevention gel in peritoneal surgery Ferric hyaluronate gel is an aqueous solution of sodium hyaluronate which has been crosslinked by the addition of a ferric chloride solution. Crosslinking between the carboxylate groups on the sodium hyaluronate and the trivalent iron (Fe 3 ) is ionic in nature, resulting in a significant increase in solution viscosity and in the intraperitoneal residence time compared with that of the starting sodium hyaluronate solution. Ferric hyaluronate gel was shown to prevent or reduce adhesion formation in preclinical animal models where sodium hyaluronate had little or no effect (Johns et al., 1997). The objectives of this study were to assess safety and to make a preliminary assessment of the efficacy of 0.5% ferric hyaluronate adhesion prevention gel (300 ml) used as an instillate in patients undergoing peritoneal cavity surgery by laparotomy as determined by a subsequent second-look laparoscopy. Materials and methods Materials The 0.5% ferric hyaluronate adhesion prevention gel was manufactured by Lifecore Biomedical Inc. (Chaska, MN, USA). The 0.5% ferric hyaluronate adhesion prevention gel is a sterile, non-pyrogenic gel of highly purified sodium hyaluronate, which is ionically crosslinked with ferric ion and adjusted to isotonicity with sodium chloride. The placebo control was lactated Ringer s solution purchased from a commercial source. Methods The study was a randomized, open-label, placebo-controlled, parallelgroup design conducted at a single centre. The study plan was approved for human evaluation by the Investigational Review Board. Patients were years old requiring peritoneal cavity surgery via laparotomy and were expected to undergo a second-look laparoscopy as part of their treatment plan from 4 12 weeks after the initial surgery. Patients with diabetes, haemochromatosis, or hepatic, renal, autoimmune, lymphatic, haematological or coagulation disorders, or those presenting with pelvic or abdominal infection were excluded from the study. Also excluded from the study were patients receiving cancer therapy, postoperative hydrotubation, anticoagulants, fibrin glue or other thrombogenic agents at the initial surgical procedure. Patients receiving any adhesion prevention adjuvant such as Interceed (TC7) absorbable adhesion barrier or Preclude surgical membrane, or those receiving any peritoneal instillate containing corticosteroid or Hyskon or those in whom any absorbable haemostat was left in the abdominal/peritoneal cavity were excluded from the study. Patients undergoing peritoneal grafting or any surgical procedure involving opening of the gastrointestinal or urinary tract, or those undergoing tubal implantation, reversal of previous surgical sterilization only, or tubal sterilization only did not participate. Within 2 weeks prior to the initial surgical procedure, the following baseline data were collected: demographic, medical and surgical history, current medications (prescription, non-prescription, and iron or iron-containing supplements), physical examination, vital signs (oral temperature, body weight and height, respiration rate, blood pressure, and pulse), and laboratory evaluations (haematology, blood chemistry, urinalysis and urine pregnancy test). Haematological evaluations consisted of haemoglobin, haematocrit, red blood cell count (RBC), white blood cell count (WBC) and differential. Blood chemistry consisted of blood urea nitrogen (BUN), creatinine, phosphorus, calcium, uric acid, total protein, albumin, total bilirubin, aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphat- ase, sodium, potassium, chloride, serum iron, and total iron binding capacity (TIBC). At the time of the initial surgical procedure, patients were assigned the next available study number corresponding to study device or control solution as determined by the randomization schedule. Prior to any adhesiolysis, the investigator assessed the overall presence, extent, and severity of adhesions at each of the following 18 anatomical sites: the anterior peritoneum, small bowel, anterior uterus, posterior uterus, omentum, large bowel, rectosigmoid portion of the large bowel, cul-de-sac (posterior), right pelvic sidewall, left pelvic sidewall, right ovary medial aspect, right ovary lateral aspect, left ovary medial aspect, left ovary lateral aspect, right tube (including fimbria), left tube (including fimbria), right ovarian fossa (posterior broad ligament) and left ovarian fossa (posterior broad ligament). The extent of adhesions was classified as localized (i.e. 50% of the site covered with adhesions) or extensive (i.e. 50% or more of the site covered with adhesions) for the above 18 sites except for the following four sites: anterior peritoneum and large bowel (difficult to visualize entire structure), and omentum and small bowel (the size precludes adequate evaluation of the extent). These sites were termed not evaluable and given an intermediate value in the calculation of an adhesion score as discussed below. The severity of adhesions was classified as mild (i.e. filmy, avascular) or severe (i.e. organized, cohesive, vascular, dense). Each patient who met all inclusion and exclusion criteria (some of which were determined during the initial operation) received 300 ml of either 0.5% ferric hyaluronate adhesion prevention gel (treatment) or lactated Ringer s solution (control). The assigned study solution was administered into the peritoneal cavity by the surgeon after the primary surgical procedure, completion of haemostasis, aspiration of all irrigants, and the removal of all packs and sponges. Four to 12 weeks after the initial surgical procedure, a second-look laparoscopic procedure was performed to re-evaluate the 18 anatomical sites as previously described during the initial surgery. The number and proportion of sites with adhesions were determined. The mean proportion was based on the number of sites with adhesions divided by the number of possible adhesion sites, which equals 18 except when sites were not present (e.g. a missing tube or ovary). The severity and extent of adhesions were evaluated. Severity was scored on a three-point scale: 0 none; 1 mild; 2 severe. Extent was scored on a three-point scale: 0 none; 1 localized; 2 extensive. A total adhesion score using the adhesion scoring method of the American Fertility Society applied to 18 anatomical sites was determined (American Fertility Society, 1988). Adhesions occurring at each of the 18 potential adhesion sites were scored as follows: No adhesion, 0; severity: mild, extent: localized, 1; severity, mild, extent: not evaluable, 2; severity: mild, extent: extensive, 4; severity: severe, extent: localized, 4; severity: severe, extent: not evaluable, 8; severity: severe, extent: extensive, 16. Scores from all potential adhesion sites were averaged to yield a total adhesion score. Safety evaluation was based on concomitant medications and conditions as well as on the type and severity of adverse events recorded throughout the study. Safety was also based on gross evaluation at second-look laparoscopy and on clinical laboratory tests performed within 2 weeks before the initial surgery, immediately prior to discharge from the hospital, and 7 to 28 days after the initial surgery. Length of hospital stay was also evaluated. The treatment and control groups were compared using Student s t-test for continuous variables and Fisher s exact test for categorical variables. Additional analyses using the Wilcoxon rank-sum test did not suggest any difference in the conclusions to be drawn. 1481

3 M.H.Thornton et al. Results A total of 23 patients were treated: 13 in the 0.5% ferric hyaluronate adhesion prevention gel (treatment) group and 10 in the lactated Ringer s solution (control) group. As shown in Table I, patients in the two groups were comparable in terms of age, height, race, and vital signs, but were marginally different in weight (P 0.048). However, the difference in weight was not significant for the 21 patients, 11 in the treatment group and 10 in the control group, who completed the study (P 0.086). As shown in Table II, the type and frequency of surgical procedures were similar for the two groups. There were no statistically Table I. Patient demographic characteristics 0.5% Ferric hyaluronate adhesion prevention gel Control (n 13) (n 10) Age (years) Mean SD Range Height (inches) Mean SD Range Weight (lb) Mean SD * Range Race (% of patients) Hispanic Black Oriental *P Table II. Type and frequency of surgical procedures Procedure 0.5% Ferric hyaluronate Control adhesion prevention gel Cystectomy Unilateral 4 0 Bilateral 0 1 Endometriomas 1 0 Tuboplasty 5 3 Myomectomy Single 3 3 Multiple 3 3 significant differences between the two groups in the number of nights spent at the hospital (2.1 1 versus 2.0 1, respectively) and the number of days to second-look laparoscopy ( versus , respectively) for the treatment and control groups. In both groups, bowel function returned to normal within 3 days, there was no evidence of ascites, and there were no cases of postoperative sepsis. Adverse events There were no serious or potentially serious adverse events reported in this study. No deaths occurred during this study and there were no study discontinuations due to an adverse event. At least one adverse event was reported by all patients in both study groups. However, no comparisons reached conventional levels (P 0.05) of significance. The three body systems with the highest patient incidence of adverse events were: body as a whole, with 100% of patients in both groups; digestive, with 53.8% of patients in the treatment group versus 50% in the control group; and nervous system, with 15.4% versus 50%, respectively. Of events affecting the body as a whole, the largest proportions were attributable to pain. Digestive system disorders were frequently attributable to nausea and constipation, while the nervous system disorders were mostly attributable to dizziness. These expected events (given that patients were undergoing anaesthesia and surgery) were generally mild to moderate and resolved spontaneously or with standard postoperative care. Laboratory tests The clinical laboratory parameters with the highest incidence of patients (15% of patients in any treatment group) who showed a shift from normal at baseline to a post-surgical high were: ALT (7.7% of patients treated with 0.5% ferric hyaluronate adhesion prevention gel versus 20.0% of those treated with lactated Ringer s control) and phosphorus (15.4% versus 30.0%, respectively). Albumin (7.7% versus 20.0%, respectively), haematocrit (7.7% versus 20.0%, respectively), and RBC (15.4% versus 10.0%, respectively), all showed a shift from normal at baseline to a post-surgical low. Most of these shifts reflected factors such as surgical trauma, infusion of various i.v. solutions and haemodilution. Efficacy Although baseline adhesion data were not significantly different between the two treatment groups, one patient in the control Table III. Number and proportion of adhesions Adhesion prevention gel (n 11) Control (n 9) Mean SD Mean SD P-value* Baseline Number of sites with adhesions Number of sites where adhesions were lysed Number of primary surgical sites Incidence of adhesions at second-look Total number of sites with adhesions Total number of sites possible Proportion *Student s t-test 1482

4 Adhesion prevention gel in peritoneal surgery group, who had a large number of adhesions at baseline (17 of 18 possible sites) which all reformed, was excluded from these analyses to make the two groups more comparable. As shown in Table III, the mean number of sites at baseline with adhesions, number of adhesions which were lysed, and the number of surgical sites (which includes adhesiolysis, surgical treatment of endometriosis, and other surgical procedures) were comparable for the two groups. However, at second-look laparoscopy, the mean number of sites with adhesions as well as the proportion of possible adhesion sites was significantly reduced in the 0.5% ferric hyaluronate adhesion prevention gel group compared with those of the control (P and P 0.023, respectively). As shown in Figure 1a and Table III, patients treated with 0.5% ferric hyaluronate adhesion prevention gel had a significantly lower number of sites with adhesions than control patients at second-look laparoscopy. Although baseline adhesion data were not significantly different between the two groups, there was a trend toward a higher number of adhesions at baseline in the control group. Therefore, the data were subdivided into those patients with fewer than five adhesions at baseline and those patients with five or more adhesions at baseline. As shown in Figure 1b and 1c, patients treated with 0.5% ferric hyaluronate adhesion prevention gel had a lower number of sites with adhesions than control patients at second-look laparoscopy for both sub-groups. The severity and extent of adhesions at baseline and at secondlook laparoscopy were also evaluated. As shown in Figure 2a and 2b, while the two groups were comparable at baseline, 0.5% ferric hyaluronate adhesion prevention gel significantly reduced the severity and extent of adhesions that did form following peritoneal cavity surgery (P and P 0.006, respectively). Adhesion formation was also assessed via a composite score adopted from the method proposed by the American Fertility Society (American Fertility Society, 1988). As shown in Figure 3a, baseline adhesion scores were comparable, and 0.5% ferric hyaluronate adhesion prevention gel significantly reduced the total adhesion score at second-look laparoscopy compared with that of the control (P 0.002). This trend also continued when the data were subdivided into those patients with fewer than five adhesions at baseline and those patients with five or more adhesions at baseline as shown in Figure 3b and 3c. abdominal cavity after laparotomy. The safety profile of 0.5% ferric hyaluronate adhesion prevention gel was comparable to that of lactated Ringer s solution (control). There were no statistically significant differences between treatment groups as to concomitant medications or adverse events. There were no clinically meaningful changes in laboratory values (including serum iron and TIBC) in either treatment group. There were no statistically significant differences between treatment groups in hospital stay. Coating the abdominal surfaces with solutions to inhibit Discussion Previous studies of adhesion prevention adjuvants where effectiveness has been demonstrated by second-look laparoscopy are primarily limited to site-specific barriers such as Interceed and Seprafilm (Diamond and The Seprafilm Adhesion Study Group, 1996; Thornton and dizerega, 1996). While these products reduce adhesions, their benefits are limited to the site of placement of the membrane or film. This study was designed to evaluate safety and efficacy of 0.5% ferric hyaluronate adhesion prevention gel in humans after peritoneal cavity surgery for reduction of adhesion formation at 18 sites throughout the entire abdomen. The 0.5% ferric hyaluronate adhesion prevention gel was shown to be easy to use and to reduce significantly the number, severity, and extent of adhesions throughout the Figure 1. Number of anatomical sites with adhesions seen at initial laparotomy and second-look laparoscopy in patients who received 300 ml of an intraperitoneal instillate of 0.5% ferric hyaluronate adhesion prevention gel or lactated Ringer s solution at the end of surgery. The data are summarized for all patients (a), and for those patients with 5 (b) and those patients with 5 (c) anatomical sites with adhesions at initial laparotomy (error bars are SEM). A * indicates a statistically significant difference (P 0.05, Students t-tests) between adhesion prevention gel and lactated Ringer s solution. 1483

5 M.H.Thornton et al. Figure 2. Severity (a) and extent (b) of adhesions seen at initial laparotomy and second-look laparoscopy in patients who received a 300 ml intraperitoneal instillate of either 0.5% ferric hyaluronate adhesion prevention gel or lactated Ringer s solution. Patients treated with 0.5% ferric hyaluronate adhesion prevention gel had significantly lower adhesion severity and extent scores compared with patients who received lactated Ringer s solution (P 0.01 for all groups; error bars are SEM). A * indicates a statistically significant difference (P 0.05, Students t-tests) between adhesion prevention gel and lactated Ringer s solution. adhesive contact of injured tissues has previously met with moderate success. Although this approach appears to be convenient and uncomplicated, no solution has provided universal benefit. A substantial body of clinical data is available to assess the benefit of crystalloid instillates, such as saline and lactated Ringer s solution, in adhesion prevention. During the early 1980s, four clinical studies were published which compared dextran with crystalloid used as instillates. A combination of these studies showed an adhesion reformation rate of approximately 80% in patients who received crystalloid instillates (dizerega and Campeau, 1994). This high rate of adhesion formation with the use of intraperitoneal instillates was confirmed by Fayez and Schneider (1987). Recently, reports appeared describing the use of crystalloid solutions to reduce adhesion formation after laparoscopic ovarian surgery. Naether and Fischer (1993) instilled ml of saline into the peritoneal cavity after laparoscopic coagulation of the ovarian surface in patients with polycystic ovarian disease. When the authors compared these patients with a previous series of patients treated in a similar fashion but without the crystalloid instillation, they found no difference in the incidence of adhesions (17% versus 19%, respectively). Gurgan et al. (1991) 1484 Figure 3. Total adhesion score at baseline and at second-look. Total adhesion score determined at the time of initial laparotomy and second-look laparoscopy in patients who received 300 ml of an intraperitoneal instillate of 0.5% ferric hyaluronate adhesion prevention gel or lactated Ringer s solution. The data are presented for all patients (a), and for those that had 5 (b) and those that had 5 (c) anatomical sites with adhesions at initial laparotomy (error bars are SEM). A * indicates a statistically significant difference (P 0.05, Students t-tests) between adhesion prevention gel and lactated Ringer s solution. instilled 150 ml of lactated Ringer s solution into the pelvis after laparoscopic electrocautery or laser vaporization of the ovarian surface in polycystic ovarian disease patients. It was found that 82% of the patients had adhesions to the ovarian surface at second-look laparoscopy (Gurgan et al., 1991). More recently, both Gurgan and Tulandi reconfirmed the failure of crystalloid (lactated Ringer s solution, 500 ml) to reduce adhesion formation in patients undergoing laparoscopic ovarian surgery (Gurgan et al., 1996; Tulandi et al., 1993). In order to significantly reduce adhesion formation and reformation, the device must effectively separate damaged surfaces during the crucial phases of post-

6 Adhesion prevention gel in peritoneal surgery surgical re-mesothelialization. The rapid rate of absorption of crystalloid solution from the peritoneal cavity (35 ml/h) may preclude its residence during the crucial turning point of adhesion formation versus normal re-mesothelialization of the peritoneal surface (Shear et al., 1965). Hyaluronic acid (HA) is a naturally occurring component of peritoneal fluid (Yung et al., 1994). Peritoneal mesothelial cells were shown to synthesize HA in vitro, and HA is thought to play a role in lubrication of cells, maintenance of the structural integrity of tissues as well as regulation of fluid retention (Asplund et al., 1993). A number of investigators previously studied the efficacy of HA solutions in adhesion prevention. Urman et al. (1991) evaluated the effectiveness of HA solution in preventing intraperitoneal adhesions in rats after carbon dioxide laser injury of the serosa. Although pre-coating of the serosa reduced de novo adhesion formation, no significant reduction of adhesions was seen when HA was added at the end of the procedure, e.g. post-treatment (Urman and Gomel, 1991). The effectiveness of reducing de novo adhesions by pre-coating prior to injuring the serosa of rats was confirmed by West et al (1996). A similar reduction of de novo adhesions in rats after serosal abrasion was noted by Shushan et al. (1994), following administration of HA as an instillate as well as application of an HA membrane after laser injury to the rat uterine horn. Diamond et al. (1996) reported the clinical effectiveness of Sepracoat hyaluronic acid coating solution used as a pre-coating solution in 245 patients undergoing laparotomy. The solution was applied upon entry into the abdominal cavity and periodically thereafter. The results reported here are with HA ionically crosslinked by ferric chloride to produce a viscous gel. In animal studies, ferric hyaluronate gel was more efficacious than HA, even when the concentration of HA was increased to produce a viscosity similar or greater than ferric hyaluronate gel (Johns et al., 1997). In addition, ferric hyaluronate gel reduced adhesion formation not only at sites of application but throughout the abdominal cavity of laboratory animals, suggesting widespread distribution by the intra-abdominal circulation (dizerega and Rodgers, 1992). The efficacy difference between the ferric hyaluronate gel and HA formulations appears to result primarily from a longer residence time in ferric hyaluronate gel relative to HA from the peritoneal cavity. This may be due to a greater tendency of ferric hyaluronate gel to adhere to the tissue or to its delayed dilution with peritoneal fluids compared with that of HA. The elimination half-life (t 1/2 ) of HA from the peritoneum in humans was estimated to be ~25.62 h. When comparing the lymphatic absorption rates of HA or ionically crosslinked HA in rats (0.38 and 0.19 µg equivalents per gram of tissue per h, respectively), it appears that the time needed to eliminate ionically crosslinked HA from the peritoneum is approximately twice that of HA. It follows, then, that the expected elimination half-life (t 1/2 ) of 0.5% ferric hyaluronate adhesion prevention gel from the peritoneal cavity of women is approximately twice that of HA, or ~51 h. In conclusion, 0.5% ferric hyaluronate adhesion prevention gel was shown to be easy to use, in this pilot study, and to reduce significantly the number, severity, and extent of adhesions after laparotomy at 18 sites throughout the abdominal cavity. The safety profile of 0.5% ferric hyaluronate adhesion prevention gel was comparable to that of lactated Ringer s solution (control). There were no statistically significant differences between treatment groups as to concomitant medications and adverse events. There were no clinically meaningful changes in laboratory values (including serum iron and TIBC) in either treatment group. Further clinical evaluation in a larger blinded study is warranted. References American Fertility Society (1988) The American Fertility Society classifications of adnexal adhesions, distal tubal occlusion, tubal occlusion secondary to tubal ligation, tubal pregnancies, Mullerian anomalies and intrauterine adhesions. Fertil. Steril., 49, Asplund, T., Vershel, M.A., Luarent, T.C. et al. (1993) Human mesotheleoma cell produce factors that stimulate the production of hyaluronan by mesothelial cells and fibroblasts. Cancer Res., 53, Diamond, M.P. and Sepracoat Adhesion Group (1996) Precoating with Sepracoat (HAL-C ) reduces postoperative de novo adhesion formation in a multicenter randomized placebo-controlled gynecologic clinical trials. J. Soc. Gynecol. Invest., 3, 90A. Diamond, M.P. and The Seprafim Adhesion Study Group (1996) Reduction of adhesions after uterine myomectomy by Seprafilm membrane (HAL-F ): a blinded, prospective, randomized, multicenter clinical study. Fertil. Steril., 66, dizerega, G.S. (1994) Contemporary adhesion prevention. Fertil. Steril., 61, dizerega, G.S. and Campeau, J.D. (1994) Use of instillates to prevent intraperitoneal adhesions: Crystalloids and dextran. Inf. Reprod. Med. Clinics N. Am., 5, dizerega, G.S. and Rodgers, K.E. (1992) Intraperitoneal Adhesions. In The Peritoneum. Springer-Verlag, New York, pp Fayez, J.A. and Schneider, P.J. (1987) Prevention of pelvic adhesion formation by different modalities of treatment. Am. J. Obstet. Gynecol., 157, Gurgan, T., Kisnisei, H., Yarali, H. et al. (1991) Evaluation of adhesion formation after laparoscopic treatment of polycystic ovarian disease. Fertil. Steril., 56, Gurgan, T., Urman, B., Yarali, H. et al. (1996) Adhesion formation and reformation after laparoscopic removal of ovarian endometriomas. J. Am. Assoc. Gynecol. Laparosc., 82, Howard, F.M. (1993) The role of laparoscopy in chronic pelvic pain: promise and pitfalls. Obstet. Gynecol. Surv., 48, Johns, D.B., Rodgers, K.E., Donahue, W.D. et al. (1997) Reduction of adhesion formation by postoperative administration of ionically cross linked hyaluronic acid. Fertil. Steril., 68, Naether, O.G.J. and Fischer, R. (1993) Adhesion formation after laparoscopic electrocoagulation of the ovarian surface in polycystic ovary patients. Fertil. Steril., 60, Rodgers, K.E., Johns, D.B., Girgis, W. et al. (1997) Reduction of adhesion formation with hyaluronic acid following peritoneal surgery in rabbits. Fertil. Steril., 67, Shear, L., Swartz, C., Shinaberger, J. et al. (1965) Kinetics of peritoneal fluid absorption in adult man. N. Engl. J. Med., 272, Shushan, A., Mor-Yosef, S., Avgar, A., et al. (1994) Hyaluronic acid for preventing experimental postoperative intraperitoneal adhesions. J. Reprod. Med., 39, Strickler, B., Blanco, J. and Fox, H.E. (1994) The gynecologic contribution to intestinal obstruction in females. J. Am. Coll. Surg., 178, Thornton, M. and dizerega, G.S. (1996) Using barriers to prevent adhesions. Contrib. Gynecol. Obstet., 41, Tulandi, T., Murray, C. and Guralnick, M. (1993) Adhesion formation and reproductive outcome after myomectomy and second-look laparoscopy. Obstet. Gynecol., 82, Urman, B. and Gomel, V. (1991) Effect of hyaluronic acid on postoperative intraperitoneal adhesion formation and reformation in the rat model. Fertil. Steril., 56, Urman, B., Gomel, V. and Jetha, N. (1991) Effect of hyaluronic acid on postoperative intraperitoneal adhesion formation in the rat model. Fertil. Steril., 56, West, J.L., Chowdhury, S.M., Sawhney, A.S. et al. (1996) Efficacy of adhesion barriers: resorbable hydrogel, oxidized regenerated cellulose and hyaluronic acid. J. Reprod. Med., 41, Yung, S., Coles, G.A., Williams, J.D. et al. (1994) The source and possible significance of hyaluronan in the peritoneal cavity. Kidney Int., 46, Received on August 28, 1997; accepted on February 23,