Anastomotic Tensile Strength Research Articles

Short cycles of remote ischemic preconditioning had no effect on tensile strength in small intestinal anastomoses: an experimental animal study

PurposeThis study aimed to investigate the effect of remote ischemic preconditioning (RIPC) on the healing of small intestinal anastomoses, evaluated by tensile strength and histologic wound healing on postoperative day 5. MethodsA total of 22 female pigs were randomized 1:1 into either an intervention or control group. The intervention group received 5 cycles of 3-minute ischemia followed by 3-minute reperfusion on the right forelimb. Two end-to-end anastomoses, a distal and a proximal, were created in the small intestine 30 and 60 min after RIPC, respectively. On postoperative day 5, the anastomoses were harvested and underwent a maximal anastomotic tensile strength (MATS) test (MATS 1–3) followed by histologic analyses. ResultsMATS 1, when a tear became visible in the serosa, was significantly increased in the proximal anastomoses of the RIPC group compared with the control group (4.91 N vs 3.83 N; P = .005). No other significant differences were found when comparing these 2 groups. ConclusionOur study showed no convincing results of RIPC on intestinal anastomotic healing to recommend its use in a general clinical setting. Further animal studies on RIPC’s effect after relative or absolute intestinal ischemia may be recommended.

Poly-ϵ-caprolactone scaffold as staple-line reinforcement of rectal anastomosis: an experimental piglet study

PurposeRectal anastomoses have a persisting high incidence of anastomotic leakage. This study aimed to assess whether the use of a poly-ϵ-caprolactone (PCL) scaffold as reinforcement of a circular stapled rectal anastomosis could increase tensile strength and improve healing compared to a control in a piglet model.MethodTwenty weaned female piglets received a stapled rectal anastomosis and were randomised to either reinforcement with PCL scaffold (intervention) or no reinforcement (control). On postoperative day five the anastomosis was subjected to a tensile strength test followed by a histological examination to evaluate the wound healing according to the Verhofstad scoring.ResultsThe tensile strength test showed no significant difference between the two groups, but histological evaluation revealed significant impaired wound healing in the intervention group.ConclusionThe incorporation of a PCL scaffold into a circular stapled rectal anastomosis did not increase anastomotic tensile strength in piglets and indicated an impaired histologically assessed wound healing.

536. PREVENTING ESOPHAGO-GASTRIC ANASTOMOTIC LEAKS; THE ROLE OF LOAD-BEARING SUTURES

Abstract The leak rate of esophago-gastric anastomosis remains at 10 to 30% despite technological advances and robotic techniques. From the moment of recovery from anaesthesia, the anastomosis is subjected to incessant distraction by the diaphragm with each inspiratory effort. It was hypothesized that eliminating all possible tension on the anastomosis during the vulnerable healing phase, by employing tension-bearing sutures between conduit and pleura, would provide the greatest opportunity for success. This study evaluated such a strategy. A prospectively maintained database of all esophagectomies performed over a 21-year period, was interrogated for the anastomotic leak rate following the introduction of a tension-elimination anastomotic technique. This consisted of securing the gastric conduit to the mediastinal pleura using load-bearing sutures inserted obliquely. When these were secured, the anastomosis became floppy, and remaining so throughout the vulnerable phase of healing, when collagenase digestion reduces anastomotic tensile strength by two-thirds. All patients had a contrast study performed between day 5 to 7 and all intra-hospital mortalities underwent autopsy to determine the cause of death. Clinical, radiological and autopsy leaks were recorded. There were 145 intra-thoracic esophago-gastric anastomoses created in 143 patients (two patients required salvage re-resection for tumour recurrence); of which 77% were male, and 65.3% were for adenocarcinoma. Fifty-five percent were stapled and 45% were hand-sewn. There was only 1 confirmed leak during the study period and 1 patient died from a mediastinal haemorrhage, which at autopsy was considered to possibly be the result of sepsis as a result of an occult anastomotic leak. The low anastomotic leak-rate is attributed to the protective effect of the load-bearing sutures; preventing any traction on the anastomosis, the most incessant source of which is the piston-like action of the diaphragm and the gripping of the diaphragmatic crura. It is intuitive that eliminating all tension during the most vulnerable phase of healing would also reduce any risk posed by minor impairments of blood supply or technical imperfections of anastomotic technique, facilitating anastomotic success.

Incorporation of a Poly-ε-Caprolactone Scaffold in a ;Circular Stapled End-To-End Small Intestine Anastomosis Does Not Have Any Adverse Effects Within 30days: A Study in Piglets.

Background. Incorporation of a poly-ε-caprolactone (PCL) scaffold in circular stapled anastomoses has been shown to increase the anastomotic tensile strength on postoperative day (POD) 5 in a pig model. The aim of this study was to investigate the effects of incorporation of a PCL scaffold in a circular stapled end-to-end small intestine anastomosis, with stricture formation and anastomotic histology as primary outcomes in a 30-day observation period. Methods. A total of 15 piglets were included. In each piglet, three circular stapled end-to-end anastomoses were made in the small intestines. Two were interventional and one was a control. On POD 10, 20, or 30, the anastomoses were subjected to in vivo intraluminal contrast study, and the index for anastomotic lumen was calculated. The anastomotic segment was resected and subjected to a tensile strength test and histological examination. Results. At POD 10, the mean ± SD value for anastomotic index was .749 ± .065 in control anastomoses and .637 ± .051 in interventional anastomosis (P = .0046), at POD 20, .541 ± .150 and .724 ± .07 (P = .051), and at POD 30, .645 ± .103 and .686 ± .057 (P = .341), respectively. No significant difference was observed in maximum tensile strength and histology at POD 30. Conclusions. The incorporation of a PCL scaffold in a circular stapled end-to-end small intestine anastomosis does not increase the risk of stricture or impair wound healing after 30days.

Evaluating Surgery Resident Technical Skills: Intestinal Anastomosis in a Porcine Model

Because work hour restrictions and technological developments such as staplers change the surgical landscape, efficient resident training methods are necessary to ensure surgical quality. This study evaluates efficacy of a porcine skills laboratory for teaching surgery residents to perform handsewn intestinal anastomoses based on a validated subjective tool and novel objective measurements. We hypothesized that resident performance would improve postintervention; junior residents would improve more than the seniors would. This prospective study was completed over a period of four months in 2015. Participants performed standardized two-layer, handsewn, end-to-end small intestine anastomosis in a live porcine model before (pretest) and after (posttest) an educational intervention. The intervention consisted of an instructional module and skills laboratory teaching session by attending surgeons. Participants were evaluated based on objective measurements of the anastomosis and blinded video evaluations using objective structured assessment of technical skills. Twenty-eight residents in a six-year general surgery program started and completed the study. The objective structured assessment of technical skills ratings demonstrated that the whole resident cohort had statistically significant improvement in pre- to posttest scores, 11.16 to 24.59 (P < 0.001). Junior and senior residents improved independently, 9.59 versus 22.53 (P < 0.001) and 13.59 versus 27.77 (P < 0.001), respectively. Finally, the cohort significantly improved in number of full-thickness Lembert sutures (2.36 vs 0.93, P = 0.001) and time to completion (31.28 vs 28.2 minutes, P = 0.046). Anastomotic leak pressure, anastomotic narrowing, and anastomotic tensile strength all trended toward improvement. A structured educational intervention, teaching intestinal anastomosis in a live porcine model produced significant improvement in residents' technical skills.

Influence of small intestine wall changes after electrically welded anastomoses of different types for the anastomotic tensile strength

The aim — to study the effect on the clinical rupture properties of the electric welded anastomosis, the morphological transformations in the wall of the small intestine after the linear and multi­point methods application.Materials and methods. In the areas of the small intestine with a diameter of 25 to 26 cm, under the conditions of a complex acute experiment on pigs, two double­row staple anastomoses with a stapler and 72 electro welded spot welds (toothed tweezers with a tip pressure of 1.8 N/mm2) and linear circular (2.1 N/mm2) as an end­to­end type. The program of the electric welding machine «Patonmed» EKVZ­300 (440 kHz) was used. Anastomoses were tested with a slow (up to 15 mm Hg/min) injection of liquid. A blind option was chosen for each type of electro welded connection: before the rupture or to the level of loss of tightness by the bracket anastomosis (24.5 mm Hg). Unbroken anastomoses were sent for histological examination.Results and discussion. All electrically welded anastomoses remained sealed at a bursting pressure of 24.5 mm Hg. A linear discontinuity was observed at 56.6 ± 9.2 mm Hg, point — at 38.2 ± 4.2 mm Hg. The thickness of the linear anastomosis compound was 0.1 to 0.16 mm and was slightly different in morphological characteristics in the segment from 1/2 to 1/3 of the circumference, in which a greater proportion of brakes and the number of gaps between connected coagulated muscle membranes was found, although in general, the integrity of the coagulation changes along the circumference persisted. The break occurred in this segment. The thickness of the point anastomosis fluctuated wavy from 0.8 to 3.4 mm. At the point of reduction of the jagged electrodes, there was a connection of the muscular membranes, a spatial orientation of the cell fragments and fibers, and the formation of a conglomerate. Perifocal muscular layers did not merge, although they were part of the coagulation conglomerate, which covered mainly the muscular and submucosa layers. Serous membranes were connected. On the example of a multipoint electrically welded junction of the intestinal walls, it is possible to estimate the margin of safety, which can have a continuous electro welded connection, and also characterize the permissible unevenness of the morphological transformations while providing clinically necessary strength and tightness parameters.Conclusions. Despite the fluctuations of the electrically welded tissues transformations depth along the ileum anastomosis circumference, the coagulated muscle layers merge presence and the integrity of the welding changes along the anastomosis line, which is based on parameters of the instrument and impulses, provides the significantly higher bursting pressure, comparing the stapled anastomosis. The tissues transformations depth as well as continuous merge density of coagulated muscles and fibers inside the linear type of welded anastomosis establishes it’s comparatively exceeded strength.

Predicting burst pressure of radiofrequency-induced colorectal anastomosis by bio-impedance measurement

The present study investigates the relationship between bio-impedance and burst pressure of colorectal anastomosis created by radiofrequency (RF)-induced tissue fusion. Colorectal anastomosis were created with ex vivo porcine colorectal segments, during which 5 levels of compression pressure were applied by a custom-made bipolar prototype, with 5 replicate experiments at each compression pressure. Instant anastomotic tensile strength was assessed by burst pressure. Bio-impedance of fused tissue was measured by Impedance Analyzer across frequency that 100 Hz to 3 MHz. Statistical analysis shows only a weak correlation between bio-impedance modulus and burst pressures at frequency of 445 kHz ( = −0.426, P = 0.099 > 0.05). In contrast, results demonstrated a highly significant negative correlation between reactance modulus and burst pressures ( = −0.812, P = 0.000 < 0.05). The decrease in mean reactance modulus with increasing burst pressures was highly significant (P = 0.019 < 0.05). The observed strong negative correlation between reactance modulus and burst pressures at frequency of 445 kHz indicates that reactance is likely to be a good index for tensile strength of RF-induced colorectal anastomosis, and should be considered for inclusion in a feedback loops in devices design.

Comparative trial assessing suture techniques and types of urinary catheters in vesicourethral anastomotic tensile strength in a porcine model

PurposeVesicourethal anastomosis (VUA) during radical prostatectomy can be achieved using various suture plication techniques. Traditionally, an indwelling urinary catheter remains in-situ to facilitate the healing process of the reconstructed VUA. Compromise or rupture of this anastomosis may lead to acute urinary leak and subsequent urinoma or stricture formation. This ex-vivo porcine model aims to evaluate VUA tensile strength using different suture techniques and catheter types. MethodsMale porcine bladders were obtained and prostatectomy was performed. The specimens were randomized and VUA were created using 3-point interrupted, 6-point interrupted or 6 point continuous 3-0 monocryl suture. 20Fr catheters were utilized, specifically varying manufacturers (A and B) and catheter balloon shapes (round versus oval). The VUA model was placed within a reproducible pulley system and graduated weights were applied until failure of the catheter balloon or the model VUA. Model failure was defined as either ‘VUA rupture’, ‘Catheter passage through VUA’ or ‘catheter failure’. ResultsTwenty consecutive porcine bladders were prepared, tested and utilized for analysis. VUA reconstructed with 3-point fixation was more likely to suffer VUA rupture (p=0.025) compared to 6-point interrupted or 6-point continuous VUA. Higher tensile pressure causing catheter balloon rupture (p=0.009) was observed for Manufacturer A. Catheters with oval-balloon shape were more likely to dislodge past the VUA without disruption of the anastomosis (p=0.002). ConclusionsDuring prostatectomy, anastomotic technique and catheter selection can significantly alter the tensile properties of the VUA. Further research is required to validate our findings in clinical models.

Different characteristics of circular staplers make the difference in anastomotic tensile strength

Anastomotic leak after gastrointestinal surgery is a severe complication associated with relevant short and long-term sequelae. Most of the anastomoses are currently performed with a surgical stapler that is required to have appropriate characteristics in order to guarantee good performances.The aim of our study was to evaluate, ex vivo, pressure resistance and tensile strength of anastomosis performed with different circular staplers available in the market.We studied 7 circular staplers of 3 different companies, 3 of them used for gastrointestinal anastomosis and 4 staplers for hemorrhoidal prolapse excision.A total of 350 anastomoses, 50 for each of the 7 staplers, were performed using healthy pig fresh intestine, then injected saline solution and recorded the leaking pressure. There were no statistically significant differences between the mean pressure necessary to induce an anastomotic leak in the various instruments (p>0.05).For studying tensile strength, we performed a total of 350 anastomoses with 7 different circular staplers on a special strong paper (Tyvek), and then recorded the maximal tensile force that could open the anastomosis. There were statistically significant differences between one brand stapler vs other 2 companies staplers about the strength necessary to open the staple line (p<0.05).In conclusion, we demonstrated that different circular staplers of three companies available in the market give comparable anastomotic pressure resistance but different tensile strengths. This is probably due to different technical characteristics.

“Tie over ring” sutureless compression based gastrointestinal anastomotic method: experimental rat model

IntroductionGiving the ever-rising trend of pediatric minimally invasive surgery besides early neonatal surgical interventions, intestinal anastomosis turns out to be a time consuming stage due to several anatomical as well as technical difficulties. A perfect bowel anastomosis method should be easy, rapid, safe and reliable in creation of bowel continuity with minimal tissue damage. In this light, sutureless anastomotic methods have been introduced, using compression based anastomosis with biofragmentable rings or powerful magnets. Accordingly, this experimental animal model study has evaluated the result of an easy, rapid intestinal sutureless anastomotic technique via simple tying over an intraluminal ring, in comparison with conventional handsewn bowel anastomosis. MethodologyThirty Wistar–Albino male rats were enrolled and small bowel was transected via a midline laparotomy. A grooved plastic ring was inserted into the ileal lumen and both intestinal cutting ends were fixed over the ring with a simple tie in the first group. On the other hand, enteroenterostomy was performed by the conventional method of handsewn anastomosis in the second group. After 14days, rats were sacrificed to evaluate for intraperitoneal adhesion and abscess formation in addition to other evidences of anastomotic leakage. Furthermore, the anastomotic site integrity, tensile strength and healing stage were assessed microscopically. ResultsThe mean operative time and intraoperative bleeding in the tie over ring group were significantly less than those in the handsewn anastomosis group. Anastomotic stricture was more common in the conventional anastomosis group while the anastomotic tensile strength was significantly higher in the tie over ring group. Histopathological healing parameters and final healing score were almost similar in both groups but mean inflammatory cell infiltration in handsewn anastomosis was significantly higher. Conclusion“Tie over ring” is a simple method of anastomosis that is feasible, fast, safe and functionally effective for bowel reconstruction in animal models that could be reconsidered in human bowel anastomosis.

Does acute alcohol intoxication interfere with colonic anastomosis wound healing?: a rat model of nondestructive colon trauma

To evaluate the effects of acute alcohol intoxication on healing of colonic anastomosis. Thirty-six rats were allocated into two groups. Animals in the alcohol (A) were given 2 mL of ethanol diluted in 0.9% saline solution to a concentration of 40% by gavage immediately before anesthesia, whereas control (C) animals received 2 mL of 0.9% saline solution via the same route. A colonic anastomosis was then performed in all animals. On postoperative days 1, 3, and 7, anastomotic breaking strength was assessed and histopathological examination was performed. Change in body weight and mortality were also evaluated. The median of anastomotic tensile strength on the postoperative day 1 was 0.09 Newtons for group A and 0.13 for group C. (p>0.05). The median of anastomotic tensile strength on the postoperative day 3 was 0.13 Newtons for group A and 0.17 for group C. (p>0.05). The median of anastomotic tensile strength on the postoperative day 7 was 0.30 Newtons for group A and 0.35 for group C. (p>0.05). There was no significant difference between the groups A and C, in the first, third or seventh POD (p>0.05), in any of the analyzed parameters. There were no statistical differences between groups in the weight. Three animals died, all from the group A. Acute alcohol intoxication did not interfere with wound healing of colonic anastomoses, although it caused early postoperative mortality.

Clinical Results Using Bioabsorbable Staple Line Reinforcement for Circular Staplers

Although linear surgical staple line reinforcement has been shown to increase anastomotic tensile strength in animal models and reduce the incidence of staple line bleeding and anastomotic leaks in colorectal surgery, the benefits of staple line reinforcement on circular stapled anastomoses in bariatric surgery remain unreported in the literature. The purpose if this study was to compare the incidence of anastomotic bleeding, leak, and stricture in patients undergoing laparoscopic gastric bypass with circular staple line reinforcements with those with no circular staple line reinforcements. Since May 2006, 138 consecutive patients (Group B) have undergone laparoscopic Roux-en-Y divided gastric bypass with a 25-mm circular stapled gastrojejunal anastomosis using GORE SEAMGUARD bioabsorbable circular staple line reinforcement (CBSG) with a mean follow up of 9 months. The incidence of anastomotic bleeding, leak, and stricture was compared with 255 similar patients (Group A) who underwent surgery before May 2006 without gastrojejunal reinforcement with a mean follow up of 22 months. The rates of anastomotic bleeding, leak, and stricture for Group B versus Group A were 0.7 per cent versus 1.1 per cent (P = 0.64); 0.7 per cent versus 1.9 per cent (P = 0.34); and 0.7 per cent versus 9.3 per cent (P = 0.0005), respectively. The use of CBSG reduced the incidence of anastomotic stricture by 93 per cent and the incidence of a composite end point of all anastomotic complications by 85 per cent. Our results indicate that the use of circular staple line reinforcement at the gastrojejunal anastomosis in patients undergoing laparoscopic gastric bypass significantly decreases the incidence of anastomotic stricture and a composite end point of all anastomotic complications. On this basis, strong consideration should be given to the routine use of CBSG staple line reinforcement in patients undergoing laparoscopic divided gastric bypass with a circular stapled gastrojejunal anastomosis.

Combination of Fibrin Glue with Growth Hormone Augments Healing of Incomplete Intestinal Anastomoses in a Rat Model of Intra-Abdominal Sepsis: A Dynamic Study

This study was devised to investigate whether fibrin glue (FG) in combination with growth hormone (GH) could have a beneficial effect at a late period (14 days) after injury. Male Wistar rats, with abdominal sepsis induced by an incomplete anastomosis, were divided into three groups. In the control group, the rats got incomplete anastomoses sutured alone; in the FG and FG/GH groups, anastomoses protection was performed with application of FG alone or in combination with GH. The anastomotic bursting pressure (ABP) was significantly higher in the FG/GH group than that of the FG group on postoperative day (POD) 5 (p <. 01), while it could not be measured from POD 7 to POD 14 because of intestinal dehiscence. There was no difference between FG and FG/GH group on POD 3 and POD 5 in anastomotic tensile strength, which was significantly higher in the FG/GH group than that of the FG group from POD 7 to POD 14 (p <. 001). Hydroxyproline content of the FG/GH group was significantly higher than that of the control from POD 3 and that of the FG group from POD 5 (p <. 05). Combination of FG with GH had a synergistic effect to improve intestinal anastomotic healing over a limited 14-day course of observation.

Effectiveness of Coagulation Factor XIII Concentrate for Reversing Loss of Tensile Strength of Rat Intestinal Anastomoses

Background: Blood coagulation factor XIII (F-XIII) promotes cross-linking of fibrin during blood coagulation. Impaired clot stabilization in patients with genetic deficiencies of F-XIII is associated with marked pathologies of wound healing. Methods: 60 rats given carbon tetrachloride underwent ileal anastomosis after which they received albumin (Alb animals) or F-XIII concentrate (F-XIII animals) immediately after surgery and daily thereafter until day 2 or 4 and were euthanized on day 3 or 5, respectively, or until day 5 and were euthanized on day 7, 10, or 21. We measured the plasma F-XIII activity and anastomotic tensile strength, followed by immunohistochemical localization of F-XIII subunit A within anastomoses. Results: On day 3, there were no significant differences between Alb and F-XIII animals for plasma F-XIII activity and tensile strength, and both groups of animals showed little immunostaining for F-XIII on anastomoses. Plasma F-XIII activities did not differ between Alb and F-XIII animals on day 5 (115.8 ± 16.8 vs. 137.3 ± 14.9%). Although the tensile strength in both groups was increased compared with that of day 3, that in F-XIII animals (129.8 ± 3.3 gf) was significantly higher than that in Alb animals (100.8 ± 5.3 gf, p = 0.014). F-XIII animals showed de novo collagen fibers and intense immunoreactivity of F-XIII in the extracellular matrix around the anastomoses. Similar differences occurred on day 7 but not days 10 and 21. Conclusions: F-XIII concentrate may accelerate the early healing process of intestinal anastomosis because of the protein’s accumulation in situ.

In vitro laser recanalization of chronically occluded prosthetic grafts.

Polytetrafluoroethylene (PTFE) and Dacron grafts were implanted in canine femoral and carotid arteries using PTFE and Prolene suture, respectively. Arteries containing occluded grafts were explanted and laser recanalization was attempted in vitro. Laser recanalization was successful in 78% of PTFE grafts compared to 30% of Dacron grafts. Recanalization was complete (residual stenosis less than 5%) in opened PTFE grafts, whereas residual stenosis averaged 60% in recanalized Dacron grafts. PTFE graft/PTFE suture anastomotic tensile strength was unchanged after recanalization, while Dacron graft/Prolene suture anastomotic tensile strength decreased significantly. In addition, anastomotic bursting pressure was significantly higher for lased PTFE grafts with PTFE sutures (300 mg Hg) compared to lased Dacron grafts with Prolene sutures (70 mm Hg). Chronically occluded PTFE grafts with PTFE suture can be safely and effectively opened by laser recanalization. In contrast, attempted laser recanalization of Dacron grafts sutured with Prolene suture is seldom successful, significantly weakens the graft artery anastomosis, and should be avoided.

Effects of diclofenac sodium on intestinal anastomotic healing

To study the possible effects of diclofenac sodium on intestinal anastomoses, 48 rabbits were submitted to surgery consisting of two single-layer ileal anastomoses performed with separate propylene 5-0 sutures. The animals were divided at random into two groups (test and control). The animals in the test group were given intramuscular injections of diclofenac sodium at the dose of 3 mg/kg body weight at 24-hour intervals, and the control animals were given injections of an identical amount of 0.9 percent saline. The animals were sacrificed on the 3rd, 7th, and 14th postoperative days for macroscopic evaluation of the peritoneal cavity and of the anastomoses, tensile strength measurement, hydroxyproline determination, and histopathologic examination. The following results were observed: anastomotic dehiscence followed by peritonitis and death in five test animals (20.83 percent) and no control animals; decreased anastomotic tensile strength on the 7th day in test animals (P less than 0.05); delayed acute inflammatory response and onset of fibroblast proliferation in the test group; and similar hydroxyproline levels in both groups. On the basis of the results obtained, we conclude that diclofenac sodium had a negative effect on intestinal anastomotic healing.

Anastomotic Tensile Strength Following In Situ Replacement of an Infected Abdominal Aortic Graft

The tensile strength and histologic features of anastomotic bonding were studied prior to and following in situ replacement of aortic vascular prostheses infected by Staphylococcus epidermidis. Sterile (n = 6) and infected (n = 19) Dacron grafts were used to replace the abdominal aorta of 25 dogs. After five weeks, grafts were explanted, and peak tensile force (measured in kilograms) required for anastomotic disruption was measured using a linear gain tensiometer. Anastomotic tensile strength (mean +/- SEM) of infected grafts (5.4 +/- 0.5 kg) was decreased when compared with that of sterile, control grafts (9.0 +/- 0.9 kg). The decreased anastomotic tensile strength of infected grafts was the result of an inflammatory aortitis adjacent to the suture line. Only grafts infected with the study strain of bacteria demonstrated signs of infection. In 19 dogs, the graft infection was treated by graft excision, antibiotic administration, and in situ graft replacement (Dacron or polytetrafluoroethylene prostheses). After five weeks and 12 weeks, anastomotic tensile strength of polytetrafluoroethylene (10.6 +/- 0.6 kg) and Dacron (10.8 +/- 0.5 kg) replacement grafts was similar to that of uninfected control grafts. In situ replacement of vascular prostheses infected by S epidermidis can result in graft healing with normal anastomotic bonding.

Primary anastomotic bonding in polytetrafluoroethylene grafts?

Previous studies have demonstrated that standard knitted and woven fabric grafts are forever dependent on the suture material for anastomotic tensile strength. Clinical experience with polytetrafluoroethylene (PTFE) and double velour knitted grafts have shown that there is extensive fibrous capsular bonding between the graft and the surrounding tissues. This would lead to increased anastomotic tensile strength. To test this theory, 34 mongrel dogs underwent replacement of their infrarenal aortas with grafts made of PTFE (10 dogs), of double velour knitted Dacron (DVD, 11 dogs), of single velour knitted Dacron (SVD, 5 dogs), and of woven Dacron (WD, 8 dogs). One anastomosis was constructed with 5-0 Prolene and the opposite anastomosis was constructed with 5-0 Dexon (average absorption time, 21 days). In five grafts each of PTFE and DVD, as well as in all eight WD grafts, the midgraft was divided and resutured with 5-0 Dexon. All grafts were harvested together with adjacent proximal and distal aorta between 3 and 10 months from the time of implantation. The tensile strength of each anastomosis was measured with a tensiometer. The mean graft-to-artery (absorbable suture) anastomotic tensile strength, in pounds, for PTFE (14.3) and DVD (12.6) was significantly higher than that for SVD (6.9) or WD (7.2) (p < 0.003). Graft-to-graft anastomotic tensile strength for PTFE (mean 17.3) was significantly better than that for DVD (mean 9.0; p < 0.03) or WD (mean 7.9; p < 0.001). Analysis of anastomotic tensile strength as a function of time revealed continued increase in PTFE in contrast to a slow decline with time in DVD. All 10 dogs in the PTFE and WD groups with graft-to-graft anastomosis (Dexon) were alive after 10 months, with intact anastomoses. Three of five dogs with DVD grafts died between 19 and 35 days following operation because of anastomotic disruption. On the basis of tensile strength and survival data, we conclude that there is evidence of improved primary anastomotic bonding in PTFE grafts and DVD grafts when contrasted to single velour knitted and woven Dacron grafts. Graft-to-graft anastomotic bonding appears superior in PTFE grafts when compared with DVD and WD.

Prostaglandins in colonic anastomotic healing.

In this study we report the effects of flurbiprofen and prostaglandin E2 on anastomotic tensile strength, collagen synthesis, and collagenolytic activity which are in a particularly fine balance in colonic healing. Colonic anastomoses were fashioned in 150 Sprague-Dawley rats which were allocated to receive either 20 mcg prostaglandin E2 in 1 ml saline, 1 ml saline alone (control) intraperitoneally for three days post-operatively, or oral 2.5 mg/kg flurbiprofen daily. Anastomotic bursting pressures, collagen content and collagenolytic activity were measured at three, six, and ten days. It was found that prostaglandin E2-treated animals had significantly weaker anastomoses at three days (102 +/- 6.1 mm Hg; m +/- SEM) compared with the control (126 +/- 7.3; P less than 0.02) or flurbiprofen group (128 +/- 4.6; P less than 0.01) with no differences at six and ten days. Collagen levels were higher in flurbiprofen-treated rats at three days (9.7 +/- 0.2 micrograms hydroxyproline/mg tissue) compared with the control (8.1 +/- 0.4 micrograms/mg; P 0.01) or prostaglandin E2 group (7.2 +/- 0.5 micrograms/mg; P 0.001). These differences were unchanged at six days but were not statistically different at ten days. Collagenolytic activity showed no differences in the three groups during the study. It is concluded that flurbiprofen enhances colonic healing with improved collagen synthesis without affecting collagenolytic activity.

Heterograft biocompatibility without proteolytic digestion

Bovine and sheep carotid heterografts (BED and S-ED) were modified by sequential treatment with 95% ethanol and 1.3% dialdehyde starch and stored in 70% ethanol. Compared with ficin digested, dialdehyde tanned bovine carotid artery (B-FD), chemical treatment produced heterografts with greater in vitro anastomotic tensile strength and significantly reduced surface clotting time. Seven of 20 canine inferior caval implants of B-ED heterografts remained patent for periods up to 4 weeks while 4 of 5 B-FD interpositions thrombosed within 2 hr. A patency rate of over 90% was obtained in canine abdominal and thoracic aorta B-ED and S-ED interpositions during a follow up period of 3 to 6 months. As arteriovenous fistulas B-ED heterografts maintained excellent patency, tolerated repetitive percutaneous puncture and exhibited self sealing capability. Microscopic examination of longterm B-ED implants showed smooth intimal surfaces with no fibrin deposition or morphologic evidence of rejection. In contrast to the ficin digested heterograft, ethanol-dialdehyde processing suppresses antigenic potential but preserves structural integrity. The end product retains components of the heterograft wall and results in a nonviable, biocompatible conduit with improved thromboresistance and greater strength.