QS68. Small Intestinel Submucosa for Intestinal Tissue Engineering
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assay. Results: Incubation at a pH of 6.0 increased the phagocytic activity of the peritoneal macrophages by 27% as compared to the cells incubated at pH of 7.4 (p.05). Incubation at a lower pH did not compromise cell survival. Conclusion: This study demonstrates that environmental acidification increases the phagocytic capacity of peritoneal macrophages. These results suggest that CO2 insufflation may specifically benefit patients with intraabdominal infections be- cause the acidic environment produced by this procedure may en- hance the ability of macrophages to clear pathogens. QS68. SMALL INTESTINEL SUBMUCOSA FOR INTESTINAL TISSUE ENGINEERING. Min Lee, Paul CY Chang, James Dunn; UCLA, Los Angeles, CA Purpose: Biodegradable scaffolds have been used for regenerating the small intestine. The aim of this study is to evaluate different layers of small intestinal submucosa (SIS) as scaffolds for intestinal regeneration in a rat model. Methods: A tubular one-ply or four-ply SIS was interposed between isolated jejunal segments in rats. The scaffolds were harvested at 2, 4, and 8 weeks after implantation, and the specimens were examined grossly and histologically. Results: Significant contractions were observed in SIS scaffolds after implan- tation. The one-ply SIS contracted to 44% of its initial length at 2 weeks and continued to contract to 6% of its initial length at 8 weeks. The contraction of four-ply SIS scaffolds was less than that of the one-ply SIS, reaching 29% of its initial length at 8 weeks. Minimal epithelial and smooth muscular regeneration was observed in the SIS scaffolds after implantation. Conclusions: A significant shrink- age was observed in the SIS scaffolds after implantation. Although the four-ply SIS contracted less than the one-ply SIS, neither scaffold supported significant amount of intestinal regeneration. QS69. TWO EXPERIMENTAL MODELS FOR GENERATING AB- DOMINAL ADHESIONS. Wolfgang B. Gaertner, Gonzalo F. Hagerman, Isaac Felemovicius, Margaret E. Bonsack, John P. Delaney; University of Minnesota, Minneapolis, MN Purpose: Students of experimental adhesion methodology have reg- ularly noted discrepant results between laboratories, probably at- tributable to variable Methods for inducing adhesions and to differ- ent criteria for quantifying results. The purpose of these experiments was to develop dependable rat models for generating abdominal adhesions that allow for objective evaluation and quantification. Methods: Two new adhesion models were compared with classical side-wall models involving cecal abrasion and peritoneal excision or abrasion. Cecal Abrasion: The cecum was exteriorized and the medial surface abraded with dry gauze over a 1 by 2 centimeter area. A similar area of the adjacent side-wall peritoneum was abraded or was excised, leaving the underlying muscle exposed. MODEL T (tissue): a 2.5 by 2.5 cm segment of full-thickness abdominal wall was excised and the overlying skin incision closed, exposing the viscera to subcutaneous tissue; MODEL M (mesh): involved removal of an identical segment, replacing the defect with a 2.5 by 2.5 cm polypropylene mesh sewn to the cut edges. This exposed the viscera directly to the mesh surface. Seven days after operation the charac- ter and extent of the adhesions were assessed at autopsy. Results were expressed as the percent area of subcutaneous tissue involved (T) or of mesh surface involved (M). For model T the percent involve- ment of the circumference of the defect edge was also recorded. The extent of omental and intestinal adhesions were evaluated individually. Results: The classical side-wall models showed incon- sistent patterns of adhesion formation and were difficult to evaluate. Every animal from both models M and T developed extensive adhe- sions. The mean coverage of mesh surface (M) was 93 percent and subcutaneous surface (T) 82 percent. In model T the mean involve- ment of the defect cut edge was 80 percent of the circumference. All model T animals had both intestinal and omental adhesions. Tenac- ity of adhesions did not differ significantly between animals or models. Conclusions: Adhesion models M and T are consistent and predictable. Each yields extensive adhesion coverage of a defined two dimensional site which allows for standardized measurement. Adhe- sion quality varies little among animals with these preparations. The relative ease of preparation and of assessment should make for ready comparison among laboratories and credible results regarding prevention strategies. Adhesion Involvement Adhesions to abdominal wall Adhesions to cecum Mean mesh or SQ surface, % area Mean cut edge, % circumference Structure(s) adhered Small bowel Omentum Cecal Abrasion Peritoneal Abrasion 50% (7/14) 50% (7/14) NA NA 4 5 Cecal Abrasion Peritoneal Excision 59% (13/22) 73% (16/22) NA NA 5 14 Model M NA NA 93% (39/39) NA 0 39 Model T NA NA 82% (15/15) 80% 15 15 SQ: subcutaneous, NA: not applicable. QS70. AUTOMATICALLY TITRATING FEEDING TO MATCH GI FUNCTION. Gerald Moss, Sr.; Rensselaer Polytechnic Institute, White Plains, NY We developed and clinically validated a regimen that continuously monitors gut activity. It automatically aspirates (“check for resid- ual”) at the feeding site every 30 seconds. The aspirated digestive juices are then returned, which contain secretory globulins, in addi- tion to conserving water and electrolytes. This restricts the feedings to remain within the patient’s limited function. The primary event in “feeding intolerance” is accumulation of foodstuff at the feeding site. Excess carbohydrate stagnates in a pool of pancreatic enzymes. Volume swells by hydrolysis and imbibing of fluid, triggering disrup- tive vagal reflexes. The already sluggish gut slows. The resulting generalized distention and malaise inhibit pulmonary mechanics and mobility. Vagal reflexes disturb cardiovascular dynamics, per- haps causing the 1:1,000 incidence of fatal bowel necrosis noted for J-tube fed patients. Conversely, tolerated nutrition stimulates and directly fuels the return of gut function. The feeding tube is aspirated alternately into one or the other of a pair of disposable chambers, and all air bubbles are efficiently vented. The chambers have an overflow at 20 ml. If inflow (feedings secretions) exceed peristaltic outflow from the feeding site, the accumulating fluid rises until it reaches the overflow level. The excess fluid is removed immediately, before it can be sensed to trigger disruptive vagal reflexes. If peristalsis accom- 296 ASSOCIATION FOR ACADEMIC SURGERY AND SOCIETY OF UNIVERSITY SURGEONS—ABSTRACTS
Transcript of QS68. Small Intestinel Submucosa for Intestinal Tissue Engineering
assay. Results: Incubation at a pH of 6.0 increased the phagocyticactivity of the peritoneal macrophages by 27% as compared to thecells incubated at pH of 7.4 (p�.05). Incubation at a lower pH did notcompromise cell survival. Conclusion: This study demonstratesthat environmental acidification increases the phagocytic capacity ofperitoneal macrophages. These results suggest that CO2 insufflationmay specifically benefit patients with intraabdominal infections be-cause the acidic environment produced by this procedure may en-hance the ability of macrophages to clear pathogens.
QS68. SMALL INTESTINEL SUBMUCOSA FOR INTESTINALTISSUE ENGINEERING. Min Lee, Paul CY Chang, JamesDunn; UCLA, Los Angeles, CA
Purpose: Biodegradable scaffolds have been used for regeneratingthe small intestine. The aim of this study is to evaluate differentlayers of small intestinal submucosa (SIS) as scaffolds for intestinalregeneration in a rat model. Methods: A tubular one-ply or four-plySIS was interposed between isolated jejunal segments in rats. Thescaffolds were harvested at 2, 4, and 8 weeks after implantation, andthe specimens were examined grossly and histologically. Results:Significant contractions were observed in SIS scaffolds after implan-tation. The one-ply SIS contracted to 44% of its initial length at 2weeks and continued to contract to 6% of its initial length at 8 weeks.The contraction of four-ply SIS scaffolds was less than that of theone-ply SIS, reaching 29% of its initial length at 8 weeks. Minimalepithelial and smooth muscular regeneration was observed in theSIS scaffolds after implantation. Conclusions: A significant shrink-age was observed in the SIS scaffolds after implantation. Althoughthe four-ply SIS contracted less than the one-ply SIS, neither scaffoldsupported significant amount of intestinal regeneration.
QS69. TWO EXPERIMENTAL MODELS FOR GENERATING AB-DOMINAL ADHESIONS. Wolfgang B. Gaertner, Gonzalo F.Hagerman, Isaac Felemovicius, Margaret E. Bonsack, JohnP. Delaney; University of Minnesota, Minneapolis, MN
Purpose: Students of experimental adhesion methodology have reg-ularly noted discrepant results between laboratories, probably at-tributable to variable Methods for inducing adhesions and to differ-ent criteria for quantifying results. The purpose of these experimentswas to develop dependable rat models for generating abdominaladhesions that allow for objective evaluation and quantification.Methods: Two new adhesion models were compared with classicalside-wall models involving cecal abrasion and peritoneal excision orabrasion. Cecal Abrasion: The cecum was exteriorized and themedial surface abraded with dry gauze over a 1 by 2 centimeter area.A similar area of the adjacent side-wall peritoneum was abraded orwas excised, leaving the underlying muscle exposed. MODEL T(tissue): a 2.5 by 2.5 cm segment of full-thickness abdominal wallwas excised and the overlying skin incision closed, exposing theviscera to subcutaneous tissue; MODEL M (mesh): involved removalof an identical segment, replacing the defect with a 2.5 by 2.5 cmpolypropylene mesh sewn to the cut edges. This exposed the visceradirectly to the mesh surface. Seven days after operation the charac-ter and extent of the adhesions were assessed at autopsy. Resultswere expressed as the percent area of subcutaneous tissue involved(T) or of mesh surface involved (M). For model T the percent involve-ment of the circumference of the defect edge was also recorded. Theextent of omental and intestinal adhesions were evaluatedindividually. Results: The classical side-wall models showed incon-sistent patterns of adhesion formation and were difficult to evaluate.Every animal from both models M and T developed extensive adhe-sions. The mean coverage of mesh surface (M) was 93 percent andsubcutaneous surface (T) 82 percent. In model T the mean involve-ment of the defect cut edge was 80 percent of the circumference. Allmodel T animals had both intestinal and omental adhesions. Tenac-ity of adhesions did not differ significantly between animals or
models. Conclusions: Adhesion models M and T are consistent andpredictable. Each yields extensive adhesion coverage of a defined twodimensional site which allows for standardized measurement. Adhe-sion quality varies little among animals with these preparations.The relative ease of preparation and of assessment should make forready comparison among laboratories and credible results regardingprevention strategies.
Adhesion Involvement
Adhesionsto
abdominalwall
Adhesionsto
cecum
Mean meshor SQ
surface, %area
Mean cutedge, %
circumference
Structure(s)adhered
Smallbowel Omentum
CecalAbrasion�PeritonealAbrasion
50%(7/14)
50%(7/14)
NA NA 4 5
CecalAbrasion�PeritonealExcision
59%(13/22)
73%(16/22)
NA NA 5 14
Model M NA NA 93%(39/39)
NA 0 39
Model T NA NA 82%(15/15)
80% 15 15
SQ: subcutaneous, NA: not applicable.
QS70. AUTOMATICALLY TITRATING FEEDING TO MATCHGI FUNCTION. Gerald Moss, Sr.; Rensselaer PolytechnicInstitute, White Plains, NY
We developed and clinically validated a regimen that continuouslymonitors gut activity. It automatically aspirates (“check for resid-ual”) at the feeding site every 30 seconds. The aspirated digestivejuices are then returned, which contain secretory globulins, in addi-tion to conserving water and electrolytes. This restricts the feedingsto remain within the patient’s limited function. The primary event in“feeding intolerance” is accumulation of foodstuff at the feeding site.Excess carbohydrate stagnates in a pool of pancreatic enzymes.Volume swells by hydrolysis and imbibing of fluid, triggering disrup-tive vagal reflexes. The already sluggish gut slows. The resultinggeneralized distention and malaise inhibit pulmonary mechanicsand mobility. Vagal reflexes disturb cardiovascular dynamics, per-haps causing the 1:1,000 incidence of fatal bowel necrosis noted forJ-tube fed patients. Conversely, tolerated nutrition stimulates anddirectly fuels the return of gut function. The feeding tube is aspiratedalternately into one or the other of a pair of disposable chambers, andall air bubbles are efficiently vented. The chambers have an overflowat 20 ml. If inflow (feedings � secretions) exceed peristaltic outflowfrom the feeding site, the accumulating fluid rises until it reaches theoverflow level. The excess fluid is removed immediately, before it canbe sensed to trigger disruptive vagal reflexes. If peristalsis accom-
296 ASSOCIATION FOR ACADEMIC SURGERY AND SOCIETY OF UNIVERSITY SURGEONS—ABSTRACTS
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