Anastomotic Tissue Research Articles

Effect of the Combination of Fibrin Glue and Growth Hormone on Intestinal Anastomoses in a Pig Model of Traumatic Shock Associated with Peritonitis

Intra-abdominal sepsis and hemorrhagic shock have been found to impair the healing of intestinal anastomoses. The present study examined whether fibrin glue (FG) and recombinant human growth hormone (GH) can improve intestinal primary anastomotic healing in a pig model of traumatic shock associated with peritonitis. Further, the study was designed to investigate the probable mechanism of these agents. Female anesthetized pigs were divided into five groups. Group sham (n = 7), pigs without traumatic shock had small bowel resection anastomoses; group control (n = 14), pigs had bowel resection anastomoses 24 h after abdominal gunshot plus exsanguination/resuscitation; group FG (n = 14); group GH (n = 14); group FG/GH (n = 14), pigs received FG, recombinant GH, or both, respectively. Recombinant GH was given daily for 7 days. Blood samples were collected daily for measurement of interleukin-6 (IL-6) and tumor necrosis factor (TNF)-alpha levels. Investigations also included adhesion formation, anastomotic bursting pressure, tensile strength, hydroxyproline (HP) content, myeloperoxidase (MPO), tumor necrosis factor (NF)-kappaB activity, and histology analysis 10 days later. A second experiment (n = 20 subjects assigned to each of the five groups) was designed to study survival during the first 20 postoperative days. Traumatic shock associated with peritonitis led to significant decreases in intestinal anastomotic bursting pressures, tensile strengths, and tissue hydroxyproline content, along with severe adhesion formation, increases in MPO activity and NF-kappaB activity, and plasma levels of tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6). Both FG and recombinant GH treatment led to early significant increases in plasma levels of TNF-alpha and IL-6. At the same time, FG alone, unlike recombinant GH alone, led to significant increases in anastomotic bursting pressures, tensile strength, and tissue HP content, along with decreases in anastomotic MPO and NF-kappaB activity and later plasma levels of TNF-a and IL-6. The FG group also developed more marked neoangiogenesis and collagen deposition on histology analysis. However, FG and recombinant GH synergistically effected improved anastomotic healing, abolishing the infaust effects promoted by recombinant GH. Adhesion formation after intestinal anastomosis could not be lowered by FG alone or by the combination of FG and recombinant GH. Both FG alone and FG/GH, in contrast to GH alone and control treatment, significantly prolonged the survival time of experimental animals. We found that FG, but not recombinant GH, could lower the risk of anastomotic leakage, improve intestinal anastomotic healing, and prolong survival in a pig model of traumatic shock associated with peritonitis. Both FG and recombinant GH synergistically effected improved intestinal anastomotic healing. It was suggested that GH could be used locally to promote intestinal anastomotic healing in intra-abdominal peritonitis.

The Effects of Sildenafil Citrate on Ischemic Colonic Anastomotic Healing in Rats: Its Relationship Between Nitric Oxide and Oxidative Stress

The purpose of this study was to examine the effects of sildenafil citrate on normal and ischemic colon anastomosis in the rat model by measuring the levels of blood and colonic tissues nitric oxide, thiobarbituric acid reactive substrates (as a marker of lipid peroxidation), and glutathione (as an antioxidant). Normal (group 1 and 3) and ischemic anastomosis (group 2 and 4) were performed in four equal rat groups (n = 14). Orally 10 mg/kg per day of sildenafil citrate therapy were applied in group 3 and group 4 after operation. Seven rats of the each group were killed on postoperative days 3 and 7. Sildenafil citrate therapy was resulted in elevated nitric oxide levels in both normal and ischemic anastomotic tissues (p < 0.0001 and p < 0.03) at postoperative day 3. Tissue thiobarbituric acid reactive substrate levels were elevated in rats with normal anastomosis by sildenafil therapy (p < 0.001) at postoperative days 3 and 7 (p < 0.05). Sildenafil therapy given to the normal anastomosis group has significantly higher tissue nitric oxide levels than the normal anastomosis group without therapy at postoperative day 7 (p < 0.001). On postoperative day 7, plasma nitric oxide levels were decreased by sildenafil citrate in rats with normal (p < 0.01) and ischemic anastomosis (p < 0.05). The beneficial effect of sildenafil citrate also was seen for erythrocyte glutathione levels in rats with normal anastomosis at postoperative day 7 and in rats with ischemic anastomosis at postoperative day 3. Our results suggest that sildenafil citrate may affect ischemic anastomotic healing due to its possible effects on nitric oxide metabolism and lipid peroxidation. However, functional implication of this agent further needs to be elucidated.

Validation of the NITI Endoluminal Compression Anastomosis Ring (EndoCAR) Device and Comparison to the Traditional Circular Stapled Colorectal Anastomosis in a Porcine Model

The purpose of this study was to determine whether the characteristics of compression anastomoses created by a new device are comparable to existing stapler technology. A total of 18 pigs were studied, and each served as its own control using a 27-mm compression device and a 29-mm stapler. Anastomoses were randomized to proximal and distal positions along the rectum and were separated by 10 cm. Six nonsurvival pigs were sacrificed at zero time to failure test the anastomoses. Twelve pigs were sacrificed at 14 days. Failure pressures, circumferences, and radiographic leak rates were determined. Anastomotic tissue was processed for matrix metalloproteinase, collagen, and elastin levels. The compression anastomoses had higher mean failure pressures than stapled anastomoses at zero time (103 vs 29.9 mm Hg). At 2 weeks, there was no difference between failure pressures (256 vs 250 mm Hg). During burst testing, 3 of the compression anastomoses failed at the anastomosis at 2 weeks, whereas none of the stapled anastomoses failed. The mean anastomotic circumference of the compression anastomoses was narrower than the stapled anastomoses (9.63 vs 11.25 cm, P = .001). There were no clinical leaks or radiographic leaks by barium enema at 2 weeks. There was no difference between matrix metalloproteinase, collagen, or elastin content based on tissue analysis. There were dense adhesions to 7 of 12 (58.3%) of the stapled anastomoses, whereas only 1 of 12 (8.3%) of the compression anastomoses had flimsy adhesions. A new compression anastomosis technique using a nickel-titanium alloy may be an advance in technology by reducing leaks and eliminating foreign material in the anastomosis.

Cellular and morphological changes during neointimal hyperplasia development in a porcine arteriovenous graft model

Implantation of a haemodialysis arteriovenous graft is often followed by the development of neointimal hyperplasia (NH) at the venous anastomosis. The nature of the proliferating cells in these lesions is not well understood. A better understanding of the cells contributing to NH is important to the development of preventive strategies. Carotid-jugular PTFE grafts were placed in 21 pigs and characterized at various time points following implantation. Venous anastomotic tissues were harvested at 1, 7, 14, 21, 28 or 49 post-operative days for histology and immunohistochemistry. Van Gieson staining of the tissues showed that NH was apparent as early as day 7 and progressed over time. Even by day 1, there were cells expressing the proliferation marker Ki-67 in the venous adventitia, but not the media, at the anastomosis. Double immunohistochemical staining showed that these cells were positive for alpha-smooth muscle actin (alpha-SMA), but negative for smooth muscle myosin heavy chain (SM MHC), suggesting that the proliferating cells were myofibroblasts rather than smooth muscle cells. By day 7, proliferating cells were abundant in the adventitia and began to appear in the media, surrounded by extracellular matrix visualized using Trichrome staining. By day 49, alpha-SMA-positive, SM MHC-negative cells were predominant in the NH, and Ki-67 staining had largely vanished. These results are consistent with the hypothesis that adventitial fibroblasts are transformed into myofibroblasts and begin to proliferate within hours after graft placement. Migration of these cells towards the vessel lumen with subsequent proliferation appears to be a major contributor to NH formation. The pivotal role of the adventitial fibroblasts in the pathogenesis of NH provides a compelling rationale for therapies that target the transformation, proliferation and migration of these cells to prevent arteriovenous graft stenosis.

Early Postoperative Oral Feeding Accelerates Upper Gastrointestinal Anastomotic Healing in the Rat Model

The benefits of early postoperative oral feeding following colonic anastomosis have previously been demonstrated. However, early postoperative oral feeding in patients with upper gastrointestinal surgery has been avoided because of concerns regarding anastomotic leakage. We investigated whether early postoperative oral feeding was advantageous for upper gastrointestinal anastomosis in comparison to parenteral feeding with a fasting period. Male Sprague-Dawley rats were subjected to the same surgical manipulation, i.e., venous catheterization, gastrostomy, and proximal jejunal anastomosis. Rats were divided into two groups: the enteral nutrition (EN) group, which received nutrients via gastrostomy as a substitute for oral feeding, and the total parental nutrition (TPN) group, which was fed via a venous catheter. Identical nutritional solutions were administered to the two groups immediately after surgery. The anastomotic bursting pressure (ABP) and the content of hydroxyproline in the anastomotic tissue were measured 5 days postoperatively. The ABP in the EN group was significantly higher than that in the TPN group (214.6 +/- 42 versus 149.5 +/- 49 mmHg; p < 0.01). The hydroxyproline content in the EN group was also significantly higher (63.5 +/- 10 versus 50.5 +/- 12 micromol/g dry tissue; p < 0.01). Early enteral feeding via gastrostomy accelerated jejunal anastomotic healing in comparison to parenteral feeding. This study clearly indicates that early oral feeding after upper gastrointestinal surgery leads to prompt anastomotic healing.

Effects of Two Conventional Preoperative Radiation Schedules on Anastomotic Healing in the Rat Colon

Background: Preoperative radiotherapy (RT) is an increasingly popular form of adjunct therapy for rectal cancer; however, little is known about its effects on matrix metalloproteinase (MMP) expression in colonic anastomotic healing. Methods: Wistar rats were irradiated to a total dose of 25 or 40 Gy. Four days after the end of RT, an end-to-end colorectal anastomosis was performed. Animals were sacrificed at 1, 3, and 7 days after the anastomosis. A control group was studied similarly, but was not irradiated. Results: No significant differences were found in peritonitis rate and anastomotic complications. The average bursting pressure and breaking strength were only reduced significantly in the rats irradiated with 40 Gy. However, the concentration and the content of hydroxyproline in anastomotic tissues were unchanged. In irradiated rats, MMP-2 and MMP-9 were significantly increased at 40 Gy, but not at 25 Gy. On the other hand, 25-Gy irradiation induced a smaller increase in the levels of the tissue inhibitors of metalloproteinase-1 compared with the controls. Conclusion: Anastomotic strength is adversely affected by high-dose fractionated preoperative RT. In contrast, preoperative RT at 25 Gy in five fractions over 5 days is safe with regard to the maintenance of wound strength in colorectal anastomosis.

Effect of Temporary Abdominal Closure on Colonic Anastomosis and Postoperative Adhesions in Experimental Secondary Peritonitis

The effect of relaparotomies and temporary abdominal closure on colonic anastomoses and postoperative adhesions is under debate. In the experiments reported here, colonic anastomosis was constructed 24 hours after cecal ligation and puncture in rats that were divided into three groups of eight animals each. The abdomen was closed primarily in groups I and II, and a Bogota bag was used for abdominal closure in group III. At 24 hours following anastomosis, relaparotomy was performed only in group II and III rats, and the abdomen was closed directly in group II; after removal of the Bogota bag in group III animals, the abdomen was closed directly. On the fifth day of anastomotic construction, bursting pressures and tissue hydroxyproline content of the anastomoses, along with peritoneal adhesions, were assessed and compared. Mean anastomotic bursting pressures and hydroxyproline contents did not differ among the groups. Median adhesion scores were significantly higher in group III than the other two groups. Relaparotomy and the type of temporary closure have no negative effect on anastomotic healing in rats with peritonitis. Temporary abdominal closure with a Bogota bag caused a significantly high rate of adhesions.

Mechanical behavior of colonic anastomosis in experimental settings as a measure of wound repair and tissue integrity

To determine the mechanical properties of anastomotic colonic tissue in experimental settings and therefore give a measure of wound healing. Thirty-six male Wistar rats were used as experimental models of anastomotic tissue integrity. On the 5th post-operative day, the tensile strength was measured by application of an axial force, providing a quantitative measure of anastomotic dehiscence and leakage. Diagrams of the load as a function of the time [P = P (t)] and of the displacement also as a function of time [Delta s = Delta s (t)] were recorded for each test, permitting the design of the load versus the displacement diagram and thus providing significant data about the critical values of anastomotic failure. Quantitative data were obtained concerning the anastomotic strength of both control specimens (healthy rats), as well as specimens from non-healthy rats for comparison. This experimental model provides an excellent method of measuring anastomotic strength. Despite the relative small number of specimens used, this method provides an accurate way of measuring wound repair. More experimental measurements need to be performed to correlate emerging tensile strength values to anastomotic failure.

Effect of Adenoviral-Mediated Transfer of Transforming Growth Factor-β1 on Colonic Anastomotic Healing

Transforming growth factor-beta1 plays a central role in colonic repair. We examined the temporal effect of vector-mediated transfer of transforming growth factor-beta1 on colonic anastomotic healing. Male Sprague-Dawley rats (n = 24) underwent transection of the distal colon and single-layer anastomosis. Proximal to the anastomosis, the colon was again transected and a colostomy was matured proximally. The distal colon was intubated with a silicone catheter, tunneled along subcutaneous tissues, and connected to a swivel apparatus for postoperative luminal infusion. Rats were randomized into four groups (n = 6 each). Two control groups received 10(10) plaque-forming units of a Type 5 E1-deleted adenovirus carrying the bacterial beta-galactosidase gene either immediately following surgery or on postoperative Day 3. The treatment groups received transforming growth factor-beta1 with the same viral construct at parallel time points. On postoperative Day 6, anastomotic bursting pressure and site were determined in situ with the anastomotic tissue subsequently harvested and analyzed by enzyme-linked immunosorbent assay for beta-galactosidase and transforming growth factor-beta1. When compared with its corresponding control, the group that received the transforming growth factor-beta1 gene on postoperative day 3 had a significantly higher bursting pressure (mmHg; 119 +/- 16 vs. 160 +/- 12, mean +/- SD; P = 0.001). While the majority of colons (5/6) from the control group burst at the anastomosis, none of the colons in the group that received transforming growth factor-beta1 on day 3 burst at the anastomotic site (P = 0.007). Beta-Galactosidase levels (pg/ml) in anastomotic tissue were significantly increased in both control groups when compared with their respective treatment groups (101 +/- 43 vs. 38 +/- 30, P = 0.01 when infused the day of surgery and 243 +/- 92 vs. 50 +/- 30, P = 0.009 when infused on day 3). Anastomotic levels of transforming growth factor-beta1 were also increased in the group receiving the transforming growth factor-beta1 gene on day 3 (214 +/- 66 vs. 135 +/- 24, P = 0.02). Gene transfer into the healing colonic anastomosis can be effectively achieved via intraluminal administration of adenoviral vectors. Transfer of transforming growth factor-beta1 increased the strength of colonic anastomoses when given at Day 3 but not at Day 0, demonstrating its diverse effects in the wound healing sequence. Thus, gene transfer of transforming growth factor-beta1 may avoid the need for a diverting stoma in cases of rectal surgery and impaired healing resulting from chemotherapy or radiation.

Temporal gene expression following prosthetic arterial grafting 12,3

Background Following prosthetic arterial grafting, cytokines and growth factors released within the perianastomotic tissues stimulate smooth muscle cell proliferation and matrix production. While much in vitro work has characterized this response, little understanding exists regarding the sequential up- and down-regulation of genes following prosthetic arterial grafting. This study evaluates temporal gene expression at the distal anastomosis of prosthetic arterial grafts using microarray analysis. Methods Expanded polytetrafluoroethylene (ePTFE) carotid interposition grafts ( n = 12) were surgically implanted into mongrel dogs. Distal anastomotic segments were harvested at 7, 14, 30, or 60 days. Contralateral carotid artery served as control. Total RNA was isolated from the anastomotic tissue and paired controls. Samples were probed with oligonucleotide microarrays consisting of approximately 10,000 human genes to analyze differential gene expression at each time point. Results Forty-nine genes were found to be up-regulated and 37 genes were found to be down-regulated at various time points. Six genes were found to be consistently up-regulated at all time intervals, including collagen type 1 α-1 and α-2, 80K-L protein (MARCKS), and osteopontin. Six genes were found to be consistently down-regulated, including smoothelin and tropomyosin 2. RT-PCR and immunohistochemistry confirmed the microarray data. Conclusions This study uses microarray analysis to identify genes that were temporally up- and down-regulated after prosthetic arterial grafting. Genes with similar patterns of expression have been identified, providing insights into related cellular pathways that may result in the formation of anastomotic intimal hyperplasia.

The Effects of Beta-Aminopropionitrile on Colonic Anastomosis in Rats

Wound contraction is a clinically important biological process because it frequently results in contractures, strictures, and stenosis. If collagen synthesis could be altered to minimize the contracture, then the outcome could be improved. Lathyrism produces poorly cross-linked collagen in healing anastomosis, keeping a larger portion of the synthesized collagen soluble. Ultimately, the amount of contracting collagen is reduced, lowering the bulk and lessening the contracture. The aim of this study was to observe the effects of a lathyrogen, beta-aminopropionitrile (BAPN), on the healing of colonic anastomosis. Thirty rats were divided into three groups. Colostomy and anastomosis were performed on all rats. Intraperitoneal saline solution (control) and either intraperitoneal (ip) or oral (po) BAPN were administered. The rats were killed 1 week later. Anastomotic healing was assessed by bursting pressure and the hydroxyproline content of the anastomotic tissues. Granulation tissue thickness, number of fibroblasts, inflammatory cells, and growing capillaries in granulation tissue per unit area were determined. Collagen fibril diameters were estimated, and spatial arrangements of fibrils were examined by an electron microscope. All results were evaluated by Mann–Whitney U-test. The analyses of anastomotic tissues from BAPN-treated rats showed a significantly reduced mean bursting pressure (158.9 ± 12.3, 171.3 ± 13.9, ip and po, respectively), hydroxyproline content (8.9 ± 2.6, 10.1 ± 2.7), granulation tissue thickness (24.3 ± 2.6, 16.1 ± 5.2), number of inflammatory cells (37.8 ± 4.3, 25 ± 4.3), fibroblasts (3.2 ± 1.1, 2.8 ± 0.7), and a significantly reduced collagen fiber diameter (15 ± 2, 20 ± 3) compared with those of control group (236.9 ± 9, 14 ± 4.4, 26.8 ± 4.8, 39 ± 2.6, 6.9 ± 1.1, and 35 ± 5, respectively). As a result, collagen fibers were flimsy, and lost their regular parallel alignment in the BAPN groups. On the other hand, a number of growing capillaries were found to be significantly increased in these groups (16.5 ± 1.1, 18.2 ± 0.7) compared to the control (6.7 ± 1.3). Thus, it is suggested that BAPN may be useful in the prevention of gastrointestinal stricture formation.

Negative Effect of Transforming Growth Factor-Beta-1 on Intestinal Anastomotic Tissue Regeneration

To examine the involvement of transforming growth factor-β₁(TGF-β₁) in intestinal anastomotic repair, we administered a TGF-β₁-neutralizing antibody to rats after operation, and then examined its influence on the healing process and interaction with other peptide growth factors. Thirty male Sprague-Dawley rats were subjected to primary anastomosis after transection of the small intestine (n = 30) and treated by intraperitoneal administration of IgG (n = 15) or the TGF-β₁ neutralizing antibody (n = 15). Treatment with the antibody against TGF-β₁ resulted in more definite mucosal growth and increased vascularity on day 5 after surgery. Augmented mRNA expression of epidermal growth factor and vascular endothelial growth factor, and an increased number of cells that expressed these peptides in granulation tissue were demonstrated by RT-PCR and immunohistochemical staining. Taken together it was indicated that TGF-β₁ has negative effects on regeneration of the bowel wall mucosa and angiogenesis in the course of intestinal anastomotic wound healing.

Regarding: “Anastomotic tissue response associated with expanded polytetrafluoroethylene access grafts constructed by using nonpenetrating clips”

Regarding: “Anastomotic tissue response associated with expanded polytetrafluoroethylene access grafts constructed by using nonpenetrating clips”

Expression and function of inducible nitric oxide synthase during rat colon anastomotic healing

Nitric oxide plays a significant but incompletely understood role in fibroblast function and cutaneous wound collagen synthesis; however, the participation of inducible nitric oxide synthase (iNOS) in gastrointestinal anastomotic healing has not been studied. Male Sprague-Dawley rats underwent single-layer left colonic anastomosis. Animals were killed at 24-hour intervals postoperatively and the anastomosis was excised. Parallel uninjured colon tissue samples were also analyzed. Reverse transcriptase-polymerase chain reaction confirmed the absence of iNOS messenger RNA in control colon and expression of the gene in anastomotic tissue on all study days. Northern hybridization demonstrated maximal iNOS messenger RNA transcription on day 1 with decreased levels on days 3 and 5. iNOS enzyme activity, measured biochemically by the conversion of [ 3H]-arginine to [ 3H]-citrulline ex vivo, was also maximal on day 1 (7.35 ± 1.34 pmol/mg protein/min [± standard error of the mean], n = 10) and decreased on days 3 (4.37 ± 2.32 pmol/mg protein/min; n = 6) and 5 (2.80 ± 0.92 pmol/mg protein/min; n = 6). Immunohistochemical staining demonstrated that (1) iNOS expression is confined to a discrete cell population in the region of the anastomosis containing inflammatory cells; (2) those cells assume a highly conserved position on the luminal edge of the proliferating scar; and (3) the iNOS-expressing cells are present throughout the fibroplastic phase of healing. To functionally assess the role of iNOS in colonic healing, rats were treated with a continuous intravenous infusion of S-methylisothiourea (a selective inhibitor of iNOS) at a dosage of 200 mg/kg/day for 5 days after anastomosis. There was a significantly reduced anastomotic bursting pressure in rats treated with the inhibitor as compared to rats treated with intravenous normal saline solution (108.4 ± 13.2 mm Hg vs. 148.4 ± 10.3 mm Hg; P <0.05). These results suggest that iNOS gene expression is induced during colonic anastomotic healing, that it is present through all phases of healing but is maximal through the inflammatory phase, and that iNOS activity is required for optimal anastomotic healing.

Stent Placement of Gastroenteric Anastomoses Formed by Magnetic Compression

To evaluate the use of stents for prolonging the patency of gastroenteric anastomoses (GEA) induced by magnet compression. Rare earth magnets were inserted perorally and serially in 15 dogs so as to mate across the gastric and jejunal walls. After magnet excretion, the resulting GEA was identified endoscopically, dilated (n = 1), and stented with bare (n = 2) or partially covered (n = 6) flared 10-mm or 12-mm Z stents. The GEA was followed at 2-4-week intervals for patency; malfunctioning shunts were irrigated, or dilated with angioplasty balloons. Gross and histologic examination of the anastomotic tissues was performed in 14 animals. Magnet pairs were excreted in 5-7 days. Of the 19 magnet placements in 15 animals, stent placement was not possible because of early GEA closure (n = 6), failure to locate (n = 2), pancreatic abscess (n = 1), and magnet perforation with peritonitis (n = 1). Estimated duration of GEA patency was 19 days after balloon dilation, 40-64 days with bare Z stents, and 58-147 days (mean, 90 days) with partially covered Z stents. Shunt function was commonly hindered by bezoars. Stent narrowing or occlusion was caused by tissue overgrowth through bare stents (n = 2), between covered stent struts and through partially detached membrane (n = 2). Serious morbidity (n = 2) was due to malpositioned magnets across the pancreas in one animal and gastric perforation in the other. One dog was euthanized because of unsuspected kidney infection. Partially covered stents significantly extend the anatomic patency rate of magnetic GEA to 7 weeks or more. Functional patency is frequently impaired by bezoars. Ongoing improvements in covered stent design should provide longer-term GEA patency.

Anastomotic tissue response associated with expanded polytetrafluoroethylene access grafts constructed by using nonpenetrating clips

Purpose: The gross, light microscopic, and scanning microscopic appearance of arterial and venous anastomoses in expanded polytetrafluoroethylene (ePTFE) access grafts constructed with nonpenetrating clips were compared with that of those constructed with polypropylene suture. We hypothesized that clip-constructed anastomoses would provide controlled approximation of native vessel intimal and medial components with the ePTFE grafts. We further hypothesized that anastomotic healing with clips would involve primarily an intimal cellular response, as compared with suture-constructed anastomoses in which cells within the media and adventitia walls participate. Methods: Femoral artery to femoral vein arteriovenous (AV) grafts were constructed in five dogs using 4-mm internal diameter ePTFE graft material. Each animal received one AV graft with anastomoses constructed by using polypropylene sutures in one leg and one AV graft with anastomoses constructed with Vascular Closure System clips in the contralateral leg. Animals were given aspirin for the duration of the study, and grafts were explanted at 5 weeks. At the time of explantation, graft segments were grossly evaluated and then underwent light and scanning electron microscopic analysis. Results: At the time of explantation, all access grafts were patent. Joining the ePTFE grafts to the native vessels with clips resulted in minimal vessel wall damage. The lumenal contours of the discontinuous approximation were smooth and without gross endothelial disruption. These observations are in contrast to the lumenal compromise and endothelial disturbance associated with the sutured anastomoses. Furthermore, hemostasis was achieved immediately in the clipped grafts, decreasing the incidence of perianastomic hematoma. Finally, cellular reconstitution occurred at the anastomotic cleft in both the sutured and the clipped junctions. The neointima exhibited an endothelial cell lining on the lumenal surface and the presence of α-smooth muscle cell actin positive cells within the subendothelial layer. Conclusion: Vascular Closure System clips are a viable alternative to suture for the approximation of ePTFE AV access grafts to native blood vessels. The use of the clips resulted in a more streamlined anastomosis, with decreased vessel wall damage, immediate hemostasis, and a trend toward shorter procedure times. (J Vasc Surg 1999;30:325-33.)

Effect of nutritional route on colonic anastomotic healing in the rat

Although early enteral feeding has been shown to benefit cutaneous healing when compared to parenteral feeding, the effect of the route of nutritional support in gastrointestinal anastomotic healing has not been defined. The aim of the present study was to determine whether the route of nutritional support influences colonic anastomotic healing. Twenty male Sprague-Dawley rats weighing 270 to 290 grams underwent identical surgical manipulation consisting of central venous catheterization, gastrostomy insertion, and distal colonic anastomosis (single-layer, inverted). Identical nutrient infusates composed of 4.25% amino acids, 25% dextrose, and vitamins were administered, with half the animals receiving the infusions via the gastrostomy and the other half via the venous catheter. Animals were killed 5 days after surgery. There were no differences in nutritional parameters between the parenterally and enterally fed groups. Colonic anastomotic bursting pressure was significantly higher in the enterally fed group (180 ± 6 vs. 150 ± 11 mm Hg; P <0.01). The measured insoluble collagen and total protein content in anastomotic tissue were enhanced in the enterally supported group. The fraction of soluble (newly synthesized) collagen did not differ between the two groups. The data demonstrate that the route of nutrient administration influences colonic anastomotic healing. The preservation of colonic structural collagen in the enteral group may improve the ability of the gut to hold sutures and thus enhance anastomotic healing.

Esophagogastric anastomotic wound healing in rats.

Esophagectomy with esophagogastric anastomosis is commonly complicated by anastomotic dehiscence. Although this is a major problem in clinical esophageal surgery, laboratory investigation of esophagogastric anastomotic wound healing has been hampered by the lack of a practical rodent model. Problems with aspiration pneumonia and anastomotic strictures hindered our previous studies in the rat. Other researchers have turned to large animal experiments, or used various upper gastrointestinal pseudoanastomotic techniques in rodents. None of these approaches has proved satisfactory. We developed a technique of side-to-side esophagogastric anastomosis in the rat, and then studied normal esophagogastric anastomotic healing in this model. Anastomoses were performed in 24 rats. Anastomotic breaking strength and hydroxyproline concentration were measured 1 and 2 weeks after surgery. Anastomotic breaking strength was 3.78 +/- 1.18 N at 1 week and 4.83 +/- 0.91 N after 2 weeks (p < 0.03). Anastomotic tissue hydroxyproline concentration was 370.6 +/- 31.2 nmol/mg at 1 week and 462.1 +/- 69.7 nmol/mg after 2 weeks (p < 0.001). Many of the problems encountered in esophagogastric anastomotic studies in the rat have been overcome using this new model.

Effect of nutritional route on colonic anastomotic healing in the rat

Although early enteral feeding has been shown to benefit cutaneous healing when compared to parenteral feeding, the effect of the route of nutritional support in gastrointestinal anastomotic healing has not been defined. The aim of the present study was to determine whether the route of nutritional support influences colonic anastomotic healing. Twenty male Sprague-Dawley rats weighing 270 to 290 grams underwent identical surgical manipulation consisting of central venous catheterization, gastrostomy insertion, and distal colonic anastomosis (single-layer, inverted). Identical nutrient infusates composed of 4.25% amino acids, 25% dextrose, and vitamins were administered, with half the animals receiving the infusions via the gastrostomy and the other half via the venous catheter. Animals were killed 5 days after surgery. There were no differences in nutritional parameters between the parenterally and enterally fed groups. Colonic anastomotic bursting pressure was significantly higher in the enterally fed group (180 +/- 6 vs. 150 +/- 11 mm Hg; P <0.01). The measured insoluble collagen and total protein content in anastomotic tissue were enhanced in the enterally supported group. The fraction of soluble (newly synthesized) collagen did not differ between the two groups. The data demonstrate that the route of nutrient administration influences colonic anastomotic healing. The preservation of colonic structural collagen in the enteral group may improve the ability of the gut to hold sutures and thus enhance anastomotic healing.

The adverse effects of octreotide on the healing of colonic anastomoses in rats.

Octreotide, a long-acting somatostatin analogue, is widely used in gastrointestinal hypersecretory states and also for endocrine tumors in an attempt to inhibit the paracrine hormones. Although it is well known that octreotide inhibits trophic and anabolic hormones, no research has been conducted on its adverse effects on wound healing. In the present study, groups of rats were given 20 mcg/kg/day octreotide and 100 mg/kg/day hydrocortisone, the latter being the negative control group, starting 5 days preoperatively. The colonic anastomoses were assessed for healing on postoperative days (PODs) 5 and 8 by determining the bursting pressure of the anastomoses, performing histopathological analysis, and measuring the hydroxyproline content of the anastomotic tissues. Octreotide was found to affect anastomotic healing negatively on both PODs 5 and 8, but the negative effect of hydrocortisone was significant only on POD 8. No significant difference was found between the adverse effects of the two agents on POD 8. These findings indicated that octreotide has an adverse effect on the healing of colonic anastomoses in rats.