New Regenerative Vascular Grafts for Hemodialysis Access: Evaluation of a Preclinical Animal Model

The purpose of this study was to evaluate a suitable animal model for the in vivo evaluation of patency and vascular tissue regeneration in small intestinal submucosa (SIS) vascular grafts for hemodialysis access. First, a 4-mm U-shaped SIS vascular graft was implanted between the internal carotid artery (CA) and the external jugular vein (JV) in five sheep and six swine. The U-shape grafts remained functional for 53 ± 4 days in sheep and 32 ± 2 days in swine. The sheep model presented exaggerated inflammation, so the swine model was selected for the in vivo study. Based on these initial results, a 4-mm C-shape SIS vascular graft with SIS circumferential reinforcement was developed to mechanically improve the vascular graft and manage complications identified during surgery in both sheep and swine. The C-shape vascular graft was implanted in a swine model (n = 3) between the CA and JV. GORE-TEX® vascular grafts were used as controls in the contralateral side of the neck. C-shape grafts remained patent for 47 ± 4 days, whereas the GORE-TEX® grafts were patent for 30 ± 15 days. The C-shape vascular graft was easier to handle during surgery, and its circumferential reinforcement improved in vivo patency, avoiding kinks in the graft after implantation. Histological results showed neovascularization and some regeneration with the alignment of endothelial cells in the vascular wall of the grafts. The model developed may be helpful in other research involving in vivo studies of vascular grafts for hemodialysis access.     

Comparison of the resistance to infection of intestinal submucosa arterial autografts versus polytetrafluoroethylene arterial prostheses in a dog model

Purpose: Prosthetic graft infection represents a most challenging complication to the vascular surgeon. Although expanded polytetrafluoroethylene (ePTFE) grafts have an acceptable patency rate, especially in the large-diameter arterial location, bacterial contamination of this material usually requires surgical removal of the graft.Methods: We compared the resistance of large-diameter ePTFE grafts and grafts constructed of small intestinal submucosa (SIS) to deliberate infection with Staphylococcus aureus. Eighteen dogs were divided into two equal groups, and the infrarenal aorta was replaced with either ePTFE or SIS graft material. One hundred million S. aureus organisms were deposited directly on the graft at the time of surgery, and the dogs were observed for 30 days.Results: One dog with an ePTFE graft died of hemorrhage from an anastomosis site at 21 days. Of the remaining eight dogs with ePTFE grafts, four had positive culture results from the removed graft material, and all had histologic evidence for persistent infection. These dogs also had chronic fever, and the average white blood cell count at day 30 was 15,600/mm³. All nine dogs with SIS grafts had patent grafts, were afebrile after the first week, had an average white blood cell count of 11,500/mm³ at 30 days (p value = NS), had negative culture results, and had the histologic appearance of graft remodeling with collagen that was free of active inflammation.Conclusions: We conclude that large-diameter arterial SIS grafts are more resistant to persistent infection with S. aureus than ePTFE grafts in this dog model of deliberate bacterial inoculation. (J VASC SURG 1994;19:465-72.)     

Small intestinal submucosa as a large diameter vascular graft in the dog

Autogenous saphenous vein and synthetic materials, such as Dacron and expanded polytetrafluoroethylene, have been used extensively as vascular grafts with moderate success. Improved success rates for vascular graft surgery may be possible if superior graft material was available. We tested the use of autogenous small intestinal submucosa (SIS) as a large diameter (10 mm) vascular graft in the infrarenal aorta of 12 dogs. One dog died with graft thrombosis within 48 hr of surgery. Nine dogs were sacrificed at various times during a 52-week post-surgical period and showed patent grafts without infection, thrombosis, intimal hyperplasia, or adverse effects upon blood pressure. There was no ultrastructural evidence of endothelial cell growth on the luminal surface of the SIS graft which was composed of a dense, non-thrombogenic, organized collagenous connective tissue. The SIS material was approximately one order of magnitude less elastic than natural aorta and showed an immediate dilatation of approximately 18% after exposure to the systemic blood pressure. However, there was no progressive dilatation during the 52-week postsurgical period. Two dogs remain alive at 8 and 52 weeks post-surgery with patent grafts as determined by positive contrast radiography and Doppler studies. We conclude that autogenous small intestinal submucosa can be successfully used as a large diameter arterial graft in the dog and is worthy of further investigation.     

Comparison of small-intestinal submucosa and expanded polytetrafluoroethylene as a vascular conduit in the presence of gram-positive contamination

OBJECTIVE: As a vascular conduit, expanded polytetrafluoroethylene (ePTFE) is susceptible to graft infection with Gram-positive organisms. Biomaterials, such as porcine small-intestinal submucosa (SIS), have been successfully used clinically as tissue substitutes outside the vascular arena. SUMMARY BACKGROUND DATA: In the present study, we compared a small-diameter conduit of SIS to ePTFE in the presence of Gram-positive contamination to evaluate infection resistance, incorporation and remodeling, morphometry, graft patency, and neointimal hyperplasia (NH) development. METHODS: Adult male mongrel pigs were randomized to receive either SIS or ePTFE (3-cm length, 6-mm diameter) and further randomized to 1 of 3 groups: Control (no graft inoculation), Staphylococcus aureus, or mucin-producing S epidermidis (each graft inoculation with 10 colonies/mL). Pressure measurements were obtained proximal and distal to the graft to create the iliac/aorta pressure ratio. Morphometric analysis of the neointima and histopathologic examinations was performed. Other outcomes included weekly WBC counts, graft incorporation, and quantitative culture of explanted grafts. RESULTS: Eighteen animals were randomized. All grafts were patent throughout the 6-week study period. Infected SIS grafts had less NH and little change in their iliac/aorta indices compared with infected ePTFE grafts. Quantitative cultures at euthanasia demonstrated no growth in either SIS group compared with 1.7 x 10(4) colonies for ePTFE S aureus and 6 x 10(2) for ePTFE S epi (each P < 0.001). All SIS grafts were incorporated. Histology demonstrated remodeling into host artery with smooth muscle and capillary ingrowth in all SIS groups. Scanning electron micrography illustrated smooth and complete endothelialization of all SIS grafts. CONCLUSIONS: Compared with ePTFE, SIS induces host tissue remodeling, exhibits a decreased neointimal response to infection, and is resistant to bacterial colonization. SIS may provide a superior alternative to ePTFE as a vascular conduit for peripheral vascular surgery.     

Small intestinal submucosa for vascular reconstruction in the presence of gastrointestinal contamination

INTRODUCTION: Surgical options for vascular reconstruction in a contaminated field are limited and include prosthetic reconstruction or ligation with extra-anatomic bypass. With prosthetic insertion, rates of graft infection and failures (pseudoaneurysms and thrombosis) are high. In the emergent situations, extra-anatomic bypass is time-consuming and complex, and it produces marginal long-term results. Small intestinal submucosa (SIS) is a cell-free collagen matrix derived from porcine small intestine. Preliminary studies have demonstrated its ability to be remodeled into host tissue. In this study, we compared SIS to polytetrafluoroethylene (PTFE) as a vascular patch for arterial repair in the presence of massive gastrointestinal contamination to evaluate graft patency, incorporation, infection, and aneurysm formation. METHODS: Adult mongrel pigs underwent general anesthesia with Isoflurane and were then randomized to 1 of 3 groups: control, contamination (colon puncture with stool contamination of the pelvis), or shock + contamination (40% blood volume for 1 hour, then resuscitation with shed blood and crystalloid, plus contamination). All groups then underwent a left common iliac arteriotomy and further randomized to a 1 x 3-cm patch angioplasty with either SIS or PTFE. All received cefotetan for 24 hours. All animals were sacrificed between 2 and 4 weeks, and necropsy was performed. Grafts were cultured, and microscopic analysis with hematoxylin and eosin and trichrome was performed. Outcomes included pulse quality (normal or diminished) compared with opposite side, graft infection, and pseudoaneurysm; all were determined by a blinded investigator. RESULTS: Forty animals were randomized, and 1 died of abdominal sepsis. All control animals had normal distal pulses, no pseudoaneurysms, and no patch infections. The pseudoaneurysm rate for the contaminated PTFE patches was 25% compared with 0% in the SIS group (P = 0.09). Patch infection occurred in 73% of all PTFE patches compared with 8% of SIS patches (P < 0.03). Organisms present in the infected grafts included Escherichia coli, Bacteroides species, and other Gram-negative enterics. Histopathology demonstrated the presence of neointima in both SIS and PTFE. Only SIS was completely incorporated, with infiltration of collagen fibrils and lymphocytes. CONCLUSIONS: SIS was associated with improved graft patency, less infection, complete incorporation, and no false aneurysm formation when compared with PTFE. This may be due to its ability to provide a durable scaffold for cellularization and tissue remodeling. This material may offer a superior alternative to more complex vascular reconstruction techniques in contaminated fields.     

Prevention of vascular graft infection by rifampin bonding to a gelatin-sealed dacron graft

This study examines the efficacy of rifampin bonding to a gelatin-sealed knitted Dacron graft to prevent perioperative bacteremic vascular graft infection. Antibiotic bonding was obtained by soaking grafts for 15 minutes in a 1 mg/ml saline solution of rifampin at 37°C. Nineteen dogs had thoracoabdominal aortic bypass: seven (group I) received a rifampin treated graft; six (group II) received an untreated gelatin-coated graft; and six (group III) received an uncoated Dacron graft. Two days later bacteremic challenge was produced by rapid intravenous injection of 5×10 ⁵ colony forming units of methicillin resistantStaphylococcus aureus.Grafts were harvested five days after this challenge and cut into 10 fragments, each submitted to bacterial counts. Results were expressed as CFU/cm ² of graft material. In group I, no graft was infected, whereas all grafts in groups II and III were infected (p<0.05). Median bacterial counts from the infected fragments (median±SD) were similar in groups II (2.5×10⁵ CFU/cm²) and III (4×10⁴ CFU/cm²). Blood cultures at time of sacrifice were negative in all dogs in group I and positive in five of six dogs in groups II and III. Cultures of liver, spleen, kidney, and lung specimens were always negative in group I and positive in 22 of 24 specimens in group II and 23 of 24 specimens in group III. Soaking a gelatin-sealed Dacron graft in rifampin solution evidently prevents early bacteremic graft infection and secondary foci of infection in this model.Presented at the Annual Meeting of the French Vascular Surgery Society, Nancy, France, May 18–19, 1990.     

Development of a small caliber vascular graft using a connective tissue tube with temporary antithrombogenicity

A connective tissue tube containing collagen fibrils and capillary blood vessels is an ideal material for artificial artery, since the collagen fibrils compose an excellent supporting framework for cell migration and proliferation and the endothelial cells of the capillary can be the origin of the endothelialization of the graft. However, its thrombogenicity has remained a problem. This experiment was designed to develop a small caliber (3mm) vascular graft using an autogenous connective tissue provided with temporary antithrombogenicity. A tube knitted of ultra-fine polyesters was implanted subcutaneously in the back of mongrel dogs for three weeks. Thus accomplished connective tissue grafts were heparinized ionically in vitro, using cross-link agents. Then the treated grafts, 5-6 cm in length and 3mm in diameter, were segmentally replaced with bilateral carotid arteries. During the follow-up period up to 55 days, 7 of 8 grafts (88%) were patent. Histological examinations revealed that there was no thrombus and the neointima formation with a lining of endotherial cells was completed, extending overall length of the grafts. Thus, newly devised hybrid type of connective tissue graft is thought to be usefull for a replacement for arteries with a small caliber.     

Multiple Oblique Illumination and High-Definition Microscopy for Breast Fine-Needle Aspirates

ABSTRACT We wished to determine whether small-intestinal submucosa (SIS) will epithelialize when used as a ureteral replacement material. An 11-mm segment of native ureter was excised from eight New Zealand White rabbits and replaced with an 11-mm porcine SIS graft, which was circumferentially wrapped around a ureteral stent. The SIS ureteral grafts were harvested at 11 days or 35 days postimplantation and examined grossly and by standard light microscopy techniques. Partial epithelialization with the ingrowth of urothelium, smooth muscle cells, and blood vessels was observed in the grafts harvested at 11 days postimplantation. The SIS ureteral grafts examined at 35 days postimplantation showed additional restructuring of the smooth muscle cell layer and more organized epithelialization in comparison to the SIS graft examined at 11 days. After 35 days of regenerative healing, elements of all three layers of the native ureter were observed within the collagen matrix of the SIS graft. No significant complications were observed, but all subjects (8/8) demonstrated mild intra-abdominal adhesions. Mild collecting system dilatations were observed in 4/4 (100%) of the animals harvested at 35 days and in 0/4 (0%) of the animals harvested at 11 days. We have this demonstrated in this preliminary study that SIS xenografts will epithelialize when used as a ureteral replacement material. The repair mechanism of these ureteral grafts occurred through a regenerative healing process rather than by scar formation. With further studies, this material may prove to be a useful treatment option in patients with ureteral injuries.     

Ureteral segment replacement using a circumferential small-intestinal submucosa xenogenic graft.

We wished to determine whether small-intestinal submucosa (SIS) will epithelialize when used as a ureteral replacement material. An 11-mm segment of native ureter was excised from eight New Zealand White rabbits and replaced with an 11-mm porcine SIS graft, which was circumferentially wrapped around a ureteral stent. The SIS ureteral grafts were harvested at 11 days or 35 days postimplantation and examined grossly and by standard light microscopy techniques. Partial epithelialization with the ingrowth of urothelium, smooth muscle cells, and blood vessels was observed in the grafts harvested at 11 days postimplantation. The SIS ureteral grafts examined at 35 days postimplantation showed additional restructuring of the smooth muscle cell layer and more organized epithelialization in comparison to the SIS graft examined at 11 days. After 35 days of regenerative healing, elements of all three layers of the native ureter were observed within the collagen matrix of the SIS graft. No significant complications were observed, but all subjects (8/8) demonstrated mild intra-abdominal adhesions. Mild collecting system dilatations were observed in 4/4 (100%) of the animals harvested at 35 days and in 0/4 (0%) of the animals harvested at 11 days. We have this demonstrated in this preliminary study that SIS xenografts will epithelialize when used as a ureteral replacement material. The repair mechanism of these ureteral grafts occurred through a regenerative healing process rather than by scar formation. With further studies, this material may prove to be a useful treatment option in patients with ureteral injuries.     

小肠黏膜下脱细胞基质修复前尿道狭窄的疗效分析

目的 探讨小肠黏膜下脱细胞基质(small intestinal submucosa,SIS)修复前尿道狭窄的可行性和有效性.方法 2009年6月至2010年8月采用4层SIS补片修复治疗尿道狭窄患者18例.患者年龄20～69岁,平均38岁;尿道狭窄段3.5～7.0 cm,平均4.6 cm;术前最大尿流率1.5～5.5 ml/s,平均3.8 ml/s.术中按需将SIS(长4.0～7.5 cm,宽 2.0 cm)植入尿道背侧缺损处,5-0可吸收线将SIS间断固定在阴茎海绵体上,SIS两侧与已剪开的狭窄段尿道作连续缝合,两端分别与尿道断端作间断吻合.结果 手术过程顺利,术后恢复好.随访6～18个月,平均10个月,患者未发生感染、排斥反应等并发症.17例排尿通畅,最大尿流率14.0～44.0 ml/s,平均25.4 ml/s.尿道造影显示尿道通畅;术后4、6周尿道镜检查示SIS移植物与周围组织分界清楚;术后14周尿道镜检查SIS已降解,修复段尿道与周围组织间限消失,黏膜光洁完整,管腔无明显狭窄;植入SIS部位活检显示黏膜表层为上皮细胞.1例尿道下裂术后患者术后5个月出现轻度尿道狭窄症状,行尿道扩张治疗.结论 利用SIS修复尿道狭窄具有创伤小、抗感染力强的特点,可作为组织工程尿道修复重建材料修复部分尿道狭窄患者.

Abstract：

Objective To investigate the feasibility of using small intestinal submucosa (SIS) graft for the repair of anterior urethral strictures. Methods From June 2009 to August 2010, 18 men (mean age, 38 yrs) with anterior urethral strictures underwent urethroplasty using a four-layer SIS as an onlay patch graft. SIS was used to augment the urethral caliber at the stricture site. The mean stricture length was 4.6 cm (range 3.5 to 7 cm). The pre-operative mean maximal flow rate was 3.8 ml/s (range 1.5 to 5.5 ml/s). The required SIS grafts (4 to 7.5 cm long and 2 cm wide) were positioned into the urethrotomy defect and were spread-fixed to the corpora cavernosa using 5-0 polyglactin interrupted sutures. Two apices of the graft were sutured to the proximal and distal apices of the urethrotomy with 5-0 polyglactin interrupted stitches. The margins of the opened urethra were sutured to the SIS patch with 5-0 polyglactin running sutures. Results The mean follow-up period was 10 mon. (range 6-18 mon.). No postoperative complication, such as infection or rejection related to the use of heterologous graft material was observed. Seventeen patients voided well postoperatively with the mean peak urine flow of 25.4 ml/s (14-44 ml/s). Cystoscopy revealed that at four weeks and six weeks, the SIS graft was well distinguishable from the normal surrounding tissue; and at 16 weeks, the urothelium was regenerated and the biomaterial was not distinguishable from the normal surrounding tissue. The squamosal epithelium was seen in the histological examination of the grafts. The remaining one patient with failed hypospadias developed a slight urethral narrowing at five months post-operatively and needed sound dilatations. Conclusions SIS matrix appears to be a safe and effective reconstructive material in selected urethral reconstructions.     

Regional variations in small intestinal submucosa evoke differences in inflammation with subsequent impact on tissue regeneration in the rat bladder augmentation model

OBJECTIVE

To examine the histological differences in the inflammatory response and regenerative outcomes of distal vs proximal porcine small intestinal submucosa (SIS) grafts in the rat bladder, as SIS from distal small intestine yields reliable and reproducible bladder regeneration, while SIS from proximal portions of small intestine does not provide similar results.

MATERIALS AND METHODS

In all, 30 Sprague‐Dawley rats underwent hemi‐cystectomy followed by anastomosis of a bladder patch of SIS prepared from either distal or proximal small intestine. After bladder harvest, immunohistochemistry was used to quantify mast cells, eosinophils, macrophages, and neutrophils (PMNs). Total cell count per unit area was compared across the time course in univariate and logistic regression modelling.

RESULTS

There were more eosinophils and mast cells in proximal SIS grafts, while there were more macrophages and PMNs in distal SIS grafts (all P < 0.05). Trichrome analysis showed increased collagen deposition in proximal SIS grafts and little smooth muscle regeneration. There was also significant graft contracture in proximal SIS grafts compared with distal SIS grafts (P < 0.05).

CONCLUSIONS

We conclude that the location of SIS origin may evoke different inflammatory responses, which results in altered bladder tissue regeneration.     

Optimal prosthetic graft design for small diameter vascular grafts

Autogenous vein and arterial grafts, such as great saphenous veins and internal mammary and radial arteries, remain the gold standard conduits for vascular reconstruction. Expanded polytetrafluoroethylene (PTFE) grafts, which exhibit little inflammatory and thrombogenic reactivity, are the most commonly used material of choice for small diameter vascular grafts when autogenous grafts are not available. Several modifications of the basic graft have been attempted to enhance graft healing of expanded PTFE grafts, and little but definite experimental and clinical improvement has been achieved so far. The technique of vascular tissue engineering, in combination with stem cell research, may hold the key for the creation of a practical and successful small diameter prosthetic graft.     

Mechanisms of ceftriaxone prophylaxis against late bacteremic vascular graft infection caused byStaphylococcus aureus in a dog model

Possible mechanisms of the prophylactic effect of ceftriaxone against late bacteremic vascular graft infection in dogs were investigated. Dogs bearing an expanded polytetrafluoroethylene graft implanted as thoracoabdominal aortic bypass for one month were exposed to transient bacteremia produced by intravenous injection of 2.6±1.8 × 10⁸ colony forming unitsStaphylococcus aureus 209P-R. To assess the effect of the antibiotic on bacteria already adherent onto the grafts, we compared the results from six untreated dogs used as controls and six dogs receiving ceftriaxone (0.5 g, intramuscularly) 90 minutes after the bacteremic challenge. The grafts were removed one week after the bacteremic challenge and cut into 10 to 15 fragments, each submitted to viable bacterial counts. The number of grafts and the number of fragments yielding bacterial growth were the same in the two groups. However, the median density of bacteria was lower (p< 0.01) in the dogs given ceftriaxone, 64 colony forming units/cm (range: 3–8,700), than in the control dogs, 585 colony forming units/cm (range: 12–64,000), suggesting that ceftriaxone had an effect on the postadherence phase of the development of infection. To assess the effect of ceftriaxone on the adherence phase we compared the results from seven untreated dogs and seven dogs receiving ceftriaxone (0.5 g intramuscularly) 90 minutes before the bacteremic challenge. The grafts were removed two hours after the bacteremic challenge. Though all the seven grafts were colonized in each group, the number of fragments yielding bacterial growth was lower (p<0.05) in the dogs given ceftriaxone (59/70) than in the control dogs (90/91). Several mechanisms may be responsible for successful antibiotic prophylaxis of graft infection, involving both early events and postadherence effects. Part of this work was presented at 27th Interscience Conference on Antimicrobial Agents and Chemotherapy, Abstract n 513, October 4–7, 1987, New York, New York.     

Morphologic evaluation of regenerated small bowel by small intestinal submucosa

Background/Purpose

Previous studies have shown small intestinal submucosa (SIS) can be used as biodegradable scaffolds in tissue engineering small intestine. The purpose of this study is to evaluate the regeneration of neointestine and its morphology using SIS.

Methods

A 2-cm tubular SIS graft from Sprague Dawley rat donors was interposed in the middle of a 6-cm ileal Thiry-Vella loop of Lewis rats, which was used to construct an ileostomy. The grafts were harvested at each of the time points ranging from 2 weeks to half a year after implantation, and native small intestine and grafts were investigated for morphology using histology and immunohistochemistry.

Results

At the early postoperative period, SIS grafts were colonized by numerous inflammatory cells. A mucosal epithelial layer began to line the luminal surface of the graft by 4 weeks, and by 12 weeks, the luminal surface was covered completely by a layer of neomucosa. Neomucosa with typical small bowel morphology was characterized by a columnar epithelial cell layer with goblet cells, Paneth cells, absorptive enterocytes, and enteroendocrine cells. Significant differences between neomucosa by 12 weeks and 24 weeks in the measurements of mucosal thickness, villus height, and crypt depth were found. The outer walls of SIS grafts were composed of distinct bundles of well-formed smooth muscle-like cells with some fibrovascular tissue.

Conclusions

This initial study suggests that tissue engineering neointestine using SIS can develop structural features of the normal intestine. Small intestinal submucosa might be a viable material in the creation of neointestine for patients suffering short bowel syndrome.     

Laser-Fused Biologic Vascular Graft Anastomoses

Tissue fusion using laser energy is a promising new technology that may improve the healing of anastomoses. This study evaluated the feasibility of using argon laser energy to fuse vascular tissue and biologic vascular prostheses (St. Jude Medical, Inc.) in a canine arteriovenous (A-V) fistula model. Five animals had 4-cm length, 3-mm internal diameter grafts (n;eq 10) placed bilaterally as side-to-side A-V interpositions from the femoral artery to femoral vein. One A-V graft was placed using argon laser energy with the vessel edges aligned by 6-0 polypropylene traction sutures at 3 to 4 mm intervals. The contralateral graft was sutured using running 6-0 polypropylene suture. Anastomoses were successfully fashioned in all animals except for episodes of delayed bleeding at two laser-fused segments (15 min and 2 hrs) and one segment in a suture control (6 days). The implants were removed to evaluate the integrity and healing of the anastomoses at 2 hrs, 8 days, and at 7, 9, and 11 weeks. In all instances, there was no evidence of anastomotic dehissance or enlargement. Histologic examination of the anastomoses revealed coapted vessel and prosthetic edges in laser-fused specimens and a limited foreign-body response to the permanent sutures in the suture controls. In the longer term specimens there was marked intimal proliferation at the venous anastomosis in all implants, with recent bilateral occlusions of the 7 and 11 week implants at the venous connection. We conclude that laser fusion of biologic vascular prostheses to autogenous vessel is possible with healing and no evidence of anastomotic dehissance. The technique may provide a method to limit development of anastomotic stenosis by eliminating the foreign body reaction. In addition, the canine arteriovenous model used in these experiments develops aggressive intimal lesions at the venous anastomosis within weeks and may be used to evaluate the effect of anastomotic technique on the development of this lesion.     

111Indium is an unreliable in vivo label for vascular endothelial cells

We studied the retention of ¹¹¹Indium-labeled canine endothelial cells on 32 grafts (16 dogs). Canine endothelial cells were harvested from the external jugular veins, grown in culture, and labeled with¹¹¹Indium oxine; 10⁶ factor VIII positive cells were inoculated on fibronectin-coated, 4 mmlD Hytrel grafts and cultured 18 hours to reach confluence. An autologous seeded graft was interposed in each of the common carotid arteries and exposed to flow for six hours.¹¹¹Indium label was measured pre- and postperfusion and corrected for decay. Twenty-five grafts from 13 dogs were available for study. Scanning electron microscopic planimetry was used to determine percent surface coverage by six mutually exclusive surface characteristics: endothelial cells, bare graft, white blood cells on graft, white blood cellson endothelium, white blood cells under endothelium, and thrombus. ¹¹¹Indium retention was compared with percent coverage by scanning electron microscopy using regression analysis.¹¹¹Indium labeling projected an erroneous retention of 41% at zero percent coverage (r=0.67; p<0.01). Multiple regression analysis revealed an equivalent distribution of¹¹¹Indium label over nonendothelial portions of the flow surface and indicated a leak rate into the circulation of 25.6% of the initial¹¹¹Indium label over six hours. We conclude that: 1)¹¹¹Indium labeling data usually overestimates endothelial cell retention; 2) an average of 4.67%/hour is lost into the general circulation; 3)¹¹¹Indium label can be found equally on surfaces of thrombus, white blood cells, and hydrophilic Hytrel graft; and 4)¹¹¹Indium labeling is not a reliable method forin vivo studies of endothelial cell retention.     

Intraoperative flow waveform analysis aids in preventing early graft failure following reconstruction of arteries of the legs

To enable early detection and treatment of vascular defects leading to early graft failure, intraoperative flow waveform analyses were carried out during lower extremity arterial reconstructions in 226 patients undergoing 102 aortoiliac/femoral and 124 femorodistal bypass grafts. Flow waveform types III or IV indicated early graft failure. These were noted in seven grafts (6.9%) in the aortoiliac/femoral position and in eight grafts (6.5%) in the femorodistal position. The main cause of the abnormal flow waveform pattern was misinterpretation of preoperative arteriographic findings in aortoiliac/femoral reconstructions and technical errors in anastomoses in femorodistal reconstructions. Of 15 grafts with an abnormal flow waveform pattern, 13 were effectively repaired with patch angioplasty, graft extension, or replacement with thrombectomy. In two grafts, the repair failed and amputation had to be done. Thus, intraoperative flow waveform analysis is a simple, useful, and safe method to detect vascular defects leading to early graft failure. Unless assessment of preoperative arteriographic findings in aortoiliac/femoral reconstructions are accurate and anastomotic techniques in femorodistal reconstructions are refined, early graft failure may occur.     

Indium 111-labeled white blood cell scans after vascular prosthetic reconstruction

The clinical value of indium 111-labeled white blood cell (WBC) scanning done after vascular graft procedures was investigated to differentiate noninfectious postoperative inflammation associated with graft incorporation from early prosthetic graft infection. Indium 111-labeled WBC scans were initially obtained in 30 patients before discharge from the hospital and during the subsequent follow-up period (334 days). Fourteen of 30 patients (47%) had normal predischarge scans that included all 10 patients who had grafts confined to the abdomen and 4 of 20 patients (20%) who had grafts arising or terminating at the femoral arteries (p less than 0.05). Sixteen of 30 patients (53%) discharged with abnormal initial indium 111 WBC scans underwent serial scanning until the scan normalized or a graft complication developed. All of the 16 patients had grafts involving the groin region. Abnormal indium 111 uptake in the femoral region continued for a mean 114 days without the development of prosthetic graft infections. The sensitivity of indium 111-labeled WBC scans for detecting wound complications was 100%, whereas the specificity was 50%. Thus, the accuracy of the test was only 53%. We conclude that (1) abnormal indium 111 WBC scans are common after graft operations involving the groin region but are unusual after vascular procedures confined to the abdomen, and (2) in the absence of clinical suspicion, the indium 111-labeled WBC scan does not reliably predict prosthetic graft infection because of the low specificity of the test in the early postoperative period.     

Local application of vancomycin for prophylaxis of graft infection: Release of vancomycin from antibiotic-bonded dacron grafts,toxicity in endothelial cell culture,and efficacy against graft infection in an animal model

Methicillin-resistant strains ofStaphylococcus epidermidis cause an increasing number of prosthetic infections. This prompted us to test the uptake of vancomycin in various graft materials in vitro, its influence on graft healing, and its efficacy against graft infection in pigs. Incubation of six different Dacron graft materials in a vancomycin solution (20 gm/L) was performed. Grafts were then placed in plasma, and samples were taken over 72 hours to determine vancomycin levels. Release of vancomycin ranged from 775 µg/cm² to 3691 µg/cm² after 1 hour of incubation. Gelatin-covered grafts increased release of vancomycin fourfold when incubation time was extended to 24 hours; uncovered grafts or the collagen-covered graft did not. Graft healing was not complicated when a vancomycin-bonded, gelatin-impregnated Dacron graft was implanted to replace the common femoral artery in pigs. Four weeks after implantation, histologic examination revealed normal development of neointima and perigraft scar tissue in the vancomycin-treated (n=4) and untreated (n=5) grafts. To test the efficacy of local vancomycin against graft infection, grafts were implanted in the groin of pigs and contaminated with 2 × 10⁷ colony-forming units ofStaphylococcus aureus. Four weeks after implantation, all grafts were infected in the untreated group (n=6), with abscess, nonincorporated graft, and detection ofS. aureus from the graft. In the treatment group (n=6) vancomycin was added to the contaminated grafts. As a carrier for the vancomycin, we used a resorbable gelatin-glycerol foam. All grafts healed without infection. The difference between the treated and untreated groups is statistically significant (p<0.05). We conclude that it may be effective to prevent graft infection with local application of vancomycin if an in situ replacement of infected graft (infected by gram-positive bacteria) is necessary or if there is a high risk of infection by methicillin-resistant staphylococci.     

Management and Outcome of Living Kidney Grafts with Multiple Arteries

Purpose Kidney allografts with multiple renal arteries (MRAs) have been used with increasing frequency since the advent of laparoscopic live donor nephrectomy. To determine if MRA grafts affect the short- and long-term outcomes of grafts and patients, we analyzed 340 grafts procured by open nephrectomy.Methods We divided the graft recipients into five groups according to the methods used for vascular reconstruction. We compared patient and graft survival, serum creatinine levels, total (rewarm) ischemic times (TIT), incidence of acute tubular necrosis (ATN), need for antihypertensive drugs, incidence of acute rejection episodes, and vascular and urologic complications, between the MRA group and a control group of patients with single-artery renal grafts.Results In patients who underwent multiple anastomoses in situ, prolonged TIT resulted in an increased incidence of ATN, but there was no significant difference between the MRA groups and the control group (P = 0.45). The incidence of vascular complications was higher in the MRA groups (P < 0.01), but there were no significant differences in the other variables among the groups.Conclusion Multiple renal artery grafts procured by open nephrectomy can be transplanted as successfully as those with single arteries, by using meticulous suturing techniques.