Late results following surgical management of vascular graft infection

Management and Clinical Outcome of Aortic Graft Infections: A Single-Center Retrospective Study

BACKGROUND

This study aimed to evaluate the outcome of various treatment options for aortic graft infection (AGI) patients and identify factors affecting their prognosis.

METHODS

The data of AGI patients from January 2008 to December 2019 were retrospectively collected and analyzed. The primary endpoints were 30-day mortality and perioperative complication-related morbidity; the secondary endpoints were re-infection (RI) rates, primary and secondary graft patency, overall mortality, duration of antibiotic therapy, and the number of antibiotic types used in treatment.

RESULTS

There was no significant difference in the 30-day mortality and perioperative-related complications between the conservative treatment, in-situ reconstruction (ISR), and extra-anatomic reconstruction (EAR) groups. The ISR group had lower re-infection rates and better overall survival rates than the EAR and conservative treatment groups. Different bypass graft conduits had no significant influence on the RI rate or primary and secondary graft patency. AGI patients infected with high-virulence pathogens had higher RI and overall mortality rates than those infected with low virulence pathogens, but this was not statistically significant. Initial procedures prior to the AGI also had no influence on the prognosis of AGI patients. Patients undergoing ISR or EAR surgery received antibiotic therapy for a longer duration than patients undergoing conservative treatment. Patients without RI received more types of antibiotics than patients with RI.

CONCLUSIONS

ISR had lower RI rates and better overall survival rates than EAR and conservative treatment and may be a better choice for patients with AGI. Several factors were found to have no influence on patients' prognosis however, further studies are required.

Improved perioperative mortality after secondary aorto-enteric fistula repair and lessons learned from a 20-year experience

BACKGROUND

Secondary aorto-enteric fistulas (SAEFs) are rare but represent one of the most challenging and devastating problems for vascular surgeons. Several issues surrounding SAEF treatment remain unresolved, including optimal surgical reconstruction and conduit choice. We performed an audit of our experience with SAEFs and highlight aspects of care that have affected outcomes over time with the intent to identify factors associated with best outcomes.

METHODS

We performed a single center, retrospective review of all consecutive SAEF repairs (1999-2019), defined as presence of a false communication between an enteric structure and pre-existing aortic graft. The primary endpoint was 30-day mortality. Secondary endpoints included incidence of complications and overall survival. Time-dependent outcome comparison was performed. Cox proportional hazards modeling and life-table analysis estimated risk and freedom from endpoints.

RESULTS

A total of 57 patients (63% male; n = 36) presented with SAEF (median age, 69 years; interquartile range [IQR], 61-74 years). Median follow-up time was 10 months (interquartile range, 3-21 months. The most common presenting symptoms were gastrointestinal bleeding (60%; n = 34) and abdominal pain (56%; n= 3 2). For the overall cohort, 30% (n = 17) underwent extra-anatomic bypass with aortic ligation, 30% (n = 17) rifampin-soaked Dacron graft, 26% (n = 15) femoral vein (eg, neoaortoiliac system), and 14% (n = 8) cryopreserved aortic allograft. The enteric communication involved the duodenum in 85% (n = 48), and a double-layer hand-sewn primary repair was most commonly employed (61%; n = 35). Thirty-day mortality was 35% (n = 20) with no significant difference between 90 days (39%; n = 22) and 180 days (42%; n = 24). Morbidity was 70% (n = 40), with gastrointestinal (30%; n = 17; leak [9%]), pulmonary (25%; n = 14), and renal (21%) complications being most common. Incidence of reoperation for any vascular and/or gastrointestinal-related complication was 56% (n = 32). One-year and 3-year survival was 54% ± 6% and 48% ± 8%, respectively. Over time, 30- and 90-day mortality improved (odds ratio, 0.1; 95% confidence interval, 0.4-0.5; P = .002) despite no change in patient factors, operative strategy, conduit choice, or morbidity rate. Prehospital history of gastrointestinal bleeding was associated with worse survival (hazard ratio, 2.0; 95% confidence interval, 1.0-3.9; P = .06); however, reconstruction strategy (in-situ vs extra-anatomic bypass), postoperative gastrointestinal and/or vascular complication, omental flap use, and preoperative endovascular aneurysm repair history were not associated with outcome.

CONCLUSIONS

In conclusion, we observed improved short-term mortality despite no significant change in patient presentation or postoperative complications. This highlights increasing institutional experience in selecting the optimal surgical strategy and improved ability to rescue patients experiencing adverse postoperative events. An individualized approach to reconstruction and conduit choice can lead to best outcomes after SAEF management when patients are treated at a high-volume aortic surgery center.

Systematic Review and Meta-Analysis on the Management of Open Abdominal Aortic Graft Infections

OBJECTIVE

Aortic graft infection (AGI) is a disastrous complication with an incidence of 0.2-6% in operated patients. With little or no high quality evidence, the best treatment option remains unclear. Therefore, the literature on the management of open abdominal AGI was systematically reviewed to determine optimal treatment.

METHODS

In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic review and meta-analysis was conducted for AGI. MEDLINE, Embase, and the Cochrane Database of Systematic Reviews were searched. Methodological quality was assessed using the Methodological Index for Non-randomised Studies (MINORS) score. Primary outcomes were 30 day mortality and one year survival. Secondary outcomes were survival, infection recurrence, limb salvage, and graft patency.

RESULTS

Of 1574 studies identified, 32 papers were included in the study. The overall quality of the studies was moderate, with an average MINORS score of 11.9. Pooled overall 30 day mortality and one year survival were 13.5% (95% CI 10.5-16.4) and 73.6% (95% CI 68.8-78.4), respectively. The lowest 30 day mortality and highest one year survival were found for in situ repair compared with extra-anatomic repair and for prosthetic grafts compared with venous grafts or arterial allografts. The infection recurrence rate was highest for prosthetic grafts.

CONCLUSIONS

There is a lack of well designed, qualitative comparative studies making conclusive recommendations impossible. The current best available data suggests that partial graft removal should be avoided and the lowest 30 day mortality and best one year survival are achieved with in situ repair using prosthetic grafts. Initiatives such as the MAGIC database to collaboratively collect prospective data are an important step forward in obtaining more solid answers on this topic.

Peripheral artery reconstructions using cryopreserved arterial allografts in infected fields

OBJECTIVE

Cryopreserved human arterial allografts are a recognized acceptable alternative for vascular reconstruction when other traditional conduits are either unavailable or contraindicated. We reviewed our experience using cryopreserved arterial allografts for peripheral artery reconstructions in contaminated and infected surgical fields.

METHODS

A single-center, retrospective review was conducted of 57 patients who underwent a peripheral vascular reconstruction using a cryopreserved arterial allograft from January 2002 through July 2017. Indications for repair included removal of infected prosthetic bypass (n = 29), revascularizations in contaminated fields (n = 11), primary arterial repair in the setting of infection (n = 10), and infected vascular closure devices (n = 7). Aorta-based repairs were excluded. Demographics, index procedural details, postoperative complications, and conduit patency were analyzed. Primary end points included conduit-related mortality and graft failure as measured by reinfection, hemorrhage, or aneurysmal degeneration. Mean follow-up for the study is 27.8 months (range, 2-125 months).

RESULTS

A total of 57 peripheral vascular reconstructions using cryopreserved arterial allografts were performed during the 15-year period. Among the 22 women and 35 men treated, the mean age was 61 years. The vascular beds involved included iliofemoral (n = 39), femoropopliteal or femoral-distal (n = 10), axillosubclavian or brachial (n = 2), mesenteric (n = 3), and carotid (n = 3) arteries. Adjunctive muscle flap coverage of the allograft conduit was performed in the majority of cases (61%; n = 35). The 30-day mortality was 9%; one death was directly related to conduit insertion. The 30-day conduit-related complication rate was 14% and included hemorrhage from the graft requiring return to the operating room (n = 4) and graft infection (n = 4). The late conduit-related complication rate was 15.8% and included graft infection (n = 1), graft thrombosis (n = 3), major amputation resulting from conduit failure (n = 1), pseudoaneurysm degeneration requiring repair (n = 2), graft hemorrhage (n = 1), and symptomatic graft stenosis (n = 1).

CONCLUSIONS

A cryopreserved arterial allograft is a useful alternative conduit for peripheral vascular reconstruction in infected or contaminated surgical fields when other autologous or prosthetic conduits are either unavailable or contraindicated. In the immediate postoperative period, these repairs demonstrate acceptable resistance to graft failure and reinfection, particularly in conjunction with adjunctive rotational muscle flap coverage. Late conduit-related complications appear to be infrequent.

Oversized Biodegradable Arterial Grafts Promote Enhanced Neointimal Tissue Formation

Most tissue-engineered arterial grafts are complicated by aneurysmal dilation secondary to insufficient neotissue formation after scaffold degradation. The optimal graft would form an organized multilayered structure with a robust extracellular matrix that could withstand arterial pressure. The purpose of the current study was to determine how oversizing a biodegradable arterial scaffold affects long-term neotissue formation. Size-matched (1.0 mm, n = 11) and oversized (1.6 mm, n = 9) electrospun polycaprolactone/chitosan scaffolds were implanted as abdominal aortic interposition grafts in Lewis rats. The mean lumen diameter of the 1.6 mm grafts was initially greater compared with the native vessel, but matched the native aorta by 6 months. In contrast, the 1.0 mm grafts experienced stenosis at 6 and 9 months. Total neotissue area and calponin-positive neotissue area were significantly greater in the 1.6 mm grafts by 6 months and similar to the native aorta. Late-term biomechanical testing was dominated by remaining polymer, but graft oversizing did not adversely affect the biomechanics of the adjacent vessel. Oversizing tissue-engineered arterial grafts may represent a strategy to increase the formation of organized neotissue without thrombosis or adverse remodeling of the adjacent native vessel by harnessing a previously undescribed process of adaptive vascular remodeling.

Management of Infected Aortic Prosthetic Grafts

The management of infected prosthetic grafts is one of the most challenging problems facing vascular surgeons. High mortality and morbidity rates with traditional treatment have led many surgeons to consider different and novel strategies. Diagnosis is usually straightforward, but occasionally is unclear even after extensive clinical and radiologic investigations. Although routine total graft excision for all infected aortic grafts is still favored by some vascular surgeons, most favor only partial graft excision if only the distal limb of the graft is involved. Placement of in situ autologous vein or cryopreserved grafts have gained popularity, and investigations are continuing regarding the use of in situ antibiotic and silver-coated prosthetic grafts. In this article the authors review the incidence and etiology of aortic graft infections, methods to prevent these complications, the diagnosis of infected aortic grafts, and lastly the management of these complicated cases, including total graft excision and partial and complete graft preservation.

Aortic Graft Infections and Aortoenteric Erosions/Fistulae

Aortic graft infections and graft enteric complications are among the most challenging problems faced by vascular surgeons. Prompt, accurate diagnosis and definitive treatment are essential if major morbidity and mortality are to be avoided. In this paper, the clinical presentation, diagnostic evaluation, and contemporary surgical management of aortic graft infections and graft enteric complications are reviewed. Traditional management techniques (extraanatomic bypass with complete graft removal) are described in detail. Newer and more controversial techniques (management of infected aortofemoral graft limb without graft removal and in situ replacement of infected aortic grafts) are discussed and their results compared with those of traditional treatment.

Surgical Treatment of Infected Aortofemoral Grafts: A Fifteen-Year Experience

During the last fifteen years, we performed a total of 855 aortofemoral re constructions. Fifteen (1.75%) grafts were surgically removed (completely or partially) owing to a severe infection (Szilagyi: Grade 3) at a mean of 66.3 months (SD ± 37.9) after their implantation. Diagnosis was always clinically evident. In 10 patients, the graft was partially removed (one or two limbs). In 3 of the 10, graft infection progressed requiring complete graft removal after a mean of 18.6 days. In the other 5 patients, the graft was removed "in toto" at the time of the first operation. In 9 cases, revascularization was accomplished by means of a "remote" takeoff reconstruction (thoracic aorta or axillary ar tery), whereas in 8 cases (3 recurred) reconstruction was performed with a "local" takeoff reconstruction (stump or aortoiliofemoral arteries). One patient was not revascularized, because the limb was already amputated.

Recurrence of infection was higher in the patients treated by partial removal of the graft (p < 0.05), even though the stump sterility was always evaluated by means of intraoperative culture. The mortality of patients with recurrence of infection was 66.6%.

Multiple operations of the femoral site were considered a factor in causing aortofemoral graft infection (p < 0.01). Diabetes was not considered a factor in causing infection (p n.s.).

Grafts with remote takeoff reconstruction have better long-term results in terms of limb salvage and survival when compared with local takeoff recon struction (p < 0.05).

In vitro efficacy of antibiotic beads in treating abdominal vascular graft infections

OBJECTIVE

Abdominal aortic vascular graft infection often involves several different organisms. Antibiotic polymethyl methacrylate (PMMA) beads may be effective in controlling infection after débridement, but bacterial species identification and antibiotic susceptibility are often not available at the time of operation, generating a need for a broad-spectrum drug combination for empirical use. We sought to determine an effective antibiotic in PMMA beads for use in abdominal vascular graft infection.

METHODS

PMMA beads were impregnated with combinations of antibiotics, consisting of daptomycin, tobramycin, and meropenem. Antibiotics were selected on the basis of activity spectrum and heat stability. Beads were placed on separate agar plates with vancomycin-resistant Enterococcus faecalis, Klebsiella pneumoniae, Staphylococcus epidermidis, and methicillin-resistant Staphylococcus aureus. Antibiotic inhibition was recorded by use of a modified agar-based disk-diffusion method.

RESULTS

Daptomycin alone was not active against K. pneumoniae (average = 0 mm). Tobramycin alone was not active against vancomycin-resistant E. faecalis, K. pneumoniae, or methicillin-resistant S. aureus. Tobramycin and daptomycin in combination had moderate broad-spectrum activity with 8- to 14-mm mean inhibition halos. Meropenem showed strong activity against all tested organisms with >15-mm mean inhibition halos. The addition of daptomycin to meropenem provided improved coverage of gram-positive organisms. The presence of tobramycin reduced the efficacy of meropenem.

CONCLUSIONS

Antibiotic PMMA beads containing 10% meropenem with 2.5% daptomycin had excellent in vitro activity against typical bacterial species associated with abdominal vascular graft infections. The addition of antibiotic beads may be a useful adjunct in managing such cases. Further studies are required to determine efficacy in clinical practice.

Prevention and treatment of aortic graft infection

Prosthetic vascular graft infection remains one of the most challenging surgical problems for vascular surgeons. This condition is classically associated with high morbidity and mortality rates. Accurate diagnosis of a vascular graft infection can typically be made based on a thorough history and physical examination; although, infrequently, an extensive radiological evaluation is necessary to establish the clinical finding. Complete graft excision and extra-anatomic bypass grafting remains a commonly accepted surgical treatment strategy. Recent clinical data have supported other treatment modalities, including the use of in situ antibiotic-impregnated graft replacement, in situ allograft replacement and in situ autologous graft replacement. This article will review the pathobiology of aortic graft infection, as well as methods to prevent a prosthetic graft infection. Furthermore, various surgical treatment modalities of aortic graft infection will be discussed.

Antibiotic-impregnated grafts for aortic reconstruction

An infected aorta, or aortic graft, is a challenge to manage. Extra-anatomical bypass followed by resection of the infected aorta has been considered standard practice. Outcomes are far from ideal and anatomical constraints make this impossible at the visceral and thoracic aorta. In situ aortic repair is an alternative and can be accomplished in most cases. Use of this technique has been tempered by concerns of graft durability and reinfection. In vitro and in vivo laboratory experiments have demonstrated antibiotics can be bound to polytetrafluoroethylene and Dacron aortic grafts. In animal models, antibiotic-soaked grafts were resistant to infection when seeded with an intravenous bacteria challenge. Purulent, infected aortic grafts created in animal models by direct bacteria inoculation could be successfully replaced in situ with infection-resistant antibiotic-soaked Dacron grafts. The antibiotic of choice is rifampin, which readily binds to commercially available, off-the-shelf gelatin- or collagen-impregnated Dacron. In humans, rifampin-soaked Dacron has not only been used to reconstruct the aorta in the face of infection, but also in elective aortic reconstruction as a prophylaxis against future infection. Outcomes from case series are difficult to interpret because of the heterogeneous nature of patients presenting with aortic infections. Thirty-day mortality ranges from 7% to 21% and morbidity from 2% to 60%. Amputations are rarely seen in these cases, but are common in extra-anatomical bypass from graft occlusion. Reinfection of the rifampin grafts are seen in 4% to 22% of patients, and 5-year survival is near 50%. In the future, the utility of rifampin-soaked Dacron will have to be tested against the emergence of antibiotic-resistant bacteria. Improvements in alternative conduits, such as cryopreserved aortic grafts, may diminish the use of antibiotic-soaked grafts, but it will remain a useful tool in the vascular surgeon's armamentarium.

Aortoenteric fistulas: CT features and potential mimics

Prompt diagnosis of aortoenteric fistulas is imperative for patient survival. The clinical signs of aortoenteric fistula include hematemesis, melena, sepsis, and abdominal pain, but the condition also may be clinically occult. Because clinical signs may not be present or may not be sufficiently specific, imaging is most often necessary to achieve an accurate diagnosis. Although no single imaging modality demonstrates the condition with sufficient sensitivity and specificity, computed tomography (CT), owing to its widespread availability and high efficiency, has become the imaging modality of choice for evaluations in the emergency setting. CT has widely variable sensitivity (40%-90%) and specificity (33%-100%) for the diagnosis of aortoenteric fistulas. To use this modality effectively for the initial diagnostic examination, radiologists must be familiar with the spectrum of CT appearances. Mimics of aortoenteric fistulas include retroperitoneal fibrosis, infected aortic aneurysm, infectious aortitis, and perigraft infection without fistulization. Differentiation is aided by the observation of ectopic gas, loss of the normal fat plane, extravasation of aortic contrast material into the enteric lumen, or leakage of enteric contrast material into the paraprosthetic space; these features are highly suggestive of aortoenteric fistula in a patient with bleeding in the gastrointestinal tract.

Aortoenteric fistula: a diagnostic dilemma

OBJECTIVE

To assess the sensitivity and specificity of computed tomography (CT) in the diagnosis of aortoenteric fistula (AEF) and to determine the most accurate CT signs of the disease.

METHODS

Hospital records were reviewed over a 20-year period. Twenty-three patients in whom a final diagnosis of AEF was made at laparotomy or autopsy were identified. Ten of these had CT performed. Twelve control cases were also collected. The 22 cases, (10 cases of AEF and 12 controls), were reviewed retrospectively by two independent readers, who were blinded to the clinical features and outcome. Each case was examined for six specific radiological findings. The outcome of other adopted investigative modalities was also examined.

RESULTS

The presence of peri-aortic ectopic gas (>2 weeks following surgery) in the context of gastrointestinal (GI) blood loss was 100% specific for AEF. If AEF was considered to be present where signs of peri-aortic infection were present in a patient with GI bleeding, CT had an overall specificity of 100% (95% confidence interval = 1.0-1.0) and sensitivity of 50%.

CONCLUSION

CT can rule in the diagnosis of AEF but cannot rule it out. CT is recommended as the first-line investigation in a stable patient with suspected AEF.

Evolution from axillofemoral to in situ prosthetic reconstruction for the treatment of aortic graft infections at a single center

OBJECTIVE

The primary purpose of this study was to analyze the clinical outcome in patients treated for aortic graft infections with in situ reconstruction (ISR). As a secondary aim, the outcomes were compared between patients who had similar clinical characteristics and extent of infection, needed total graft excision, and had either ISR or axillofemoral reconstruction (AXFR).

METHODS

117 consecutive patients treated for aortic graft infection over a 20 year period from January 1981 to December 2001 were identified. 52 patients had prosthetic ISR, 49 had AXFR, and 16 had other reconstructions. The ISR patients treated with total (n = 35) or partial (n = 17) graft excision comprised the primary analysis. A second analysis was done between 34 ISR and 43 AXFR patients (non-concurrent groups), as stated above. Primary outcome measures were early and late procedure-related death, primary graft patency and limb loss. Secondary outcomes were operative morbidity, patient survival, and graft reinfection rates.

RESULTS

There were 40 males and 12 females with a mean age of 69 years treated with ISR. 43 patients had Rifampin-soaked grafts and 39 had omental flap or other autogenous coverage. Operative morbidity occurred in 23 patients (44%). There were 4 early and no late procedure-related deaths after a median follow up of 3.4 years (range, 2 months to 9.6 years). Primary patency and limb salvage rates at 5 years were 89% and 100%, respectively. Graft reinfection occurred in 6 patients (11.5%) and was not associated with procedure-related death. In the comparative analysis, the procedure-related death rate for patients treated with ISR was not different than those treated with AXFR (9% versus 23%; P = 0.11). There was a significant improvement in primary patency between ISR and AXFR at 5 years (89% versus 48%; P = .01). Limb salvage was 100% for ISR and 89% for AXFR at 5 years (P = .06). The incidence of graft reinfection was similar in both groups: 11% for ISR and 17% for AXFR (P = .28). Major complications or procedure-related deaths occurred in 12 patients after ISR (30%) and 26 patients (60%) after AXFR (P < .04).

CONCLUSION

ISR is a safe and effective alternative in the treatment of select patients with aortic graft infection. Graft reinfection occurred in 11.5% of the patients. The graft patency and limb salvages rates are excellent.

Improved outcomes in the recent management of secondary aortoenteric fistula

OBJECTIVE

We reviewed the presentation, management, and late events in a recent experience with aortic graft-enteric communications (secondary aortoenteric fistula) to identify variables associated with poor outcomes.

METHODS

Since 1991, 29 patients (19 men, 10 women; mean age, 70) presented with a secondary aortoenteric fistula. The duration from aortic graft implantation to aortoenteric fistula development ranged from 8 months to 180 months (mean, 47 months). Presenting symptoms included gastrointestinal bleeding (n = 25), sepsis and retroperitoneal abscess (n = 3), and ruptured para-anastomotic aneurysm (n = 1). One third (10/29) of patients were hypotensive at presentation. Repair was accomplished by graft excision with axillobifemoral bypass (17 simultaneous, 8 staged), graft excision with in situ deep vein replacement (n = 2), or graft excision with rifampin-treated prosthetic replacement (n = 2). Mean follow-up was 51 months, and the incidence of late events was reported by life table methods.

RESULTS

The operative (< or = 30-day) mortality rate was 21%, with shock at presentation (P < .01), the need for preoperative transfusion (P < .01), and use of suprarenal aortic clamping during aortoenteric fistula repair (P = .03) associated with lethal outcome. Cumulative mortality related to aortoenteric fistula management was only 24% within an overall 5-year survival rate of 61%. Freedom from recurrent infection or amputation was 86% and 88% at 5 years, respectively, and assisted graft patency was 79%. Presence of staphylococcal species in 22% of patients and occasional operative findings of adjacent perigraft "biofilm" suggests that underlying indolent graft infection may contribute to the development of aortoenteric fistula in some cases.

CONCLUSION

Outcomes associated with aortoenteric fistula repair were surprisingly favorable in the absence of preoperative hemodynamic instability.

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.

Intra-abdominal aortic graft infection: complete or partial graft preservation in patients at very high risk

BACKGROUND

Total graft excision with in situ or extra-anatomic revascularization is considered mandatory to treat infection involving the body of aortic grafts. We present a series of nine patients with this complication and such severe comorbid medical illnesses or markedly hostile abdomens that traditional treatments were precluded. In these patients selective complete or partial graft preservation was used.

METHODS

Over the past 20 years we have treated nine infected infrarenal aortic prosthetic grafts with complete or partial graft preservation, because excision of the graft body was not feasible. In all nine patients infection of the main body of the aortic graft was documented at computed tomography or surgery. Essential adjuncts included percutaneous or operative drain placement into retroperitoneal abscess cavities and along the graft, with instillation of antibiotics three times daily, repeated debridement of infected groin wounds, and intravenous antibiotic therapy for at least 6 weeks.

RESULTS

One patient with purulent groin drainage treated with complete graft preservation died of sepsis. One patient with groin infection treated with complete graft preservation initially did well, but ultimately required total graft excision 5 months later, after clinical improvement. In four patients complete graft preservation was successful; two patients required excision of an occluded infected limb of the graft; and one patient underwent subtotal graft excision, leaving a graft remnant on the aorta, and axillopopliteal bypass. In summary, seven of nine patients survived hospitalization after complete or partial graft preservation; amputation was avoided in all but one patient; and no recurrent infection developed over mean follow-up of 7.6 years (range, 2-15 years).

CONCLUSIONS

Although contrary to conventional concepts, partial or complete graft preservation combined with aggressive drainage and groin wound debridement is an acceptable option for treatment of infection involving an entire aortic graft in selected patients with prohibitive risks for total graft excision. This treatment may be compatible with long-term survival and protracted absence of signs or symptoms of infection.

Graft-preserving treatment for vascular graft infected with Staphylococcus aureus with antibiotic-releasing porous apatite ceramic in the rabbit

OBJECTIVE

This study was undertaken to investigate whether infection of a vascular graft with Staphylococcus aureus can be treated in situ by applying antibiotic-loaded porous apatite ceramic, in a rabbit model.

METHODS

Teicoplanin (TEIC) was loaded onto a beta-tricalcium phosphate (TCP) block, a type of porous apatite ceramic. The activity of TEIC released from the antibiotic-loaded TCP block was examined in vivo. A vascular graft was patched onto the abdominal aorta in 24 rabbits, and S aureus was applied directly on it. Seven days postoperatively, each rabbit underwent repeat laparotomy, and retroperitoneal abscess around the prosthetic vascular patch was debrided. Animals were divided into four groups of 6 rabbits each. In group 1 only debridement was carried out. In groups 2 and 3, solution containing 40 or 60 mg of TEIC, respectively, was applied to the prosthetic vascular patch. In group 4, an antibiotic-loaded TCP block (63 +/- 6.6 mg of TEIC) was placed around the graft. Three weeks after the second operation, the graft, the tissue around it, and arterial blood were collected and cultured.

RESULTS

TEIC activity was maintained for 28 days in vivo. In group 1, bacterial cultures of the prosthetic vascular graft and the tissue around it were positive in 5 animals and negative in 1 animal (infection rate, 83%). In both groups 2 and 3, cultures were positive in 3 animals and negative in 3 animals (infection rate, 50%). In group 4, cultures were negative in all animals (infection rate, 0%). Blood cultures were negative in all animals. Infection rate in group 4 was significantly lower than that in group 1 (P =.03), and was also lower than that in groups 2 and 3, but the difference was not significant.

CONCLUSIONS

Use of slow-release antibiotic loaded onto a TCP block, along with debridement, may control infection in vascular grafts in situ, averting the necessity to remove the graft.

Detection of aortoenteric fistula with helical CT

We describe a case of a patient with symptoms suggestive of secondary aortoenteric fistula (AEF). Extravasation of contrast medium from the aorta into the lumen of the small bowel was definitive evidence of AEF. The role of abdominal CT performed without oral contrast is discussed.

Laser-induced shock waves enhance sterilization of infected vascular prosthetic grafts

BACKGROUND AND OBJECTIVE

Bacteria that cause infection of vascular prosthetic grafts produce an exopolysaccharide matrix known as biofilm. Growth in biofilms protects the bacteria from leukocytes, antibodies and antimicrobial drugs. Laser-generated shock waves (SW) can disrupt biofilms and increase drug penetration. This study investigates the possibility of increasing antibiotic delivery and sterilization of vascular prosthetic graft.

STUDY DESIGN/MATERIALS AND METHODS

Strains of Staphylococcus epidermidis and S. aureus were isolated from infected prosthetic grafts obtained directly from patients. Dacron grafts were inoculated with the isolated bacteria, which were allowed to form adherent bacterial colonies. The colonized grafts underwent the following treatments: (a) antibiotic (vancomycin) alone; (b) antibiotic and SW (c) saline only; and (d) saline and SW. Six hours after treatment, the grafts were sonicated, the effluent was cultured and the colony forming units (CFU) were counted.

RESULTS

CFU recovered from control grafts colonized by S. epidermidis were comparable: saline, 3.05 x 10(8) and saline+SW 3.31 x 10(8). The number of S. epidermidis CFU diminished to 7.61 x 10(6) after antibiotic treatment but the combined antibiotic+SW treatment synergistically decreased CFU number to 1.27 x 10(4) (P<0.001). S. aureus showed a higher susceptibility to the antibiotic: 2.26 x 10(6) CFU; antibiotic +SW treatment also had an incremental effect: 8.27 x 10(4) CFU (P<0.001).

CONCLUSIONS

This study demonstrates that laser-generated shock waves have no effects alone, but can enhance the effectiveness of antibiotics against bacteria associated with prosthetic vascular graft biofilms, suggesting that this treatment may be of value as adjunctive therapy for prosthetic graft infections.

Abdominal aortic reconstruction in infected fields: early results of the United States cryopreserved aortic allograft registry

OBJECTIVE

Aortic reconstructions for primary graft infection (PGI), mycotic aneurysm (MA), and aortic graft-enteric erosion (AEE) bear high morbidity and mortality rates, and current treatment options are not ideal. Cryopreserved grafts have been implanted successfully in infected fields and may be suitable for abdominal aortic reconstructions. Registry data from several institutions were compiled to examine results of cryopreserved aortic allograft (CAA) placement.

METHODS

The experience of 31 institutions was reviewed for CAAs inserted from March 4, 1999, to August 23, 2001. Indications for CAA, organisms, mortality, and complications were identified.

RESULTS

Fifty-six patients, 43 men and 13 women, with a mean age of 66 years (range, 44 to 90 years) had in situ aortic replacement with CAA. Indications for CAA placement were PGI in 43 patients (77%), MA in seven (14%), AEE in four (7%), and aortic reconstruction with concomitant bowel resection in two (4%). Infectious organisms were identified in 33 patients (59%); the most frequent organism was Staphylococcus aureus in 17 (52%). Thirty-one patients (55%) needed an additional cryopreserved segment for reconstruction. The mean follow-up period was 5.3 months (range, 1 to 22 months). One patient died in the operating room, and the 30-day surgical mortality rate was 13% (7/56). Seven additional patients died during the follow-up period, yielding an overall mortality rate of 25% (14 patients). Two patients (4%) had graft-related mortality as the result of hemorrhage from the CAA and persistent infection. Graft-related complications included persistent infection with perianastomotic hemorrhage in five patients (9%), graft limb occlusion in five (9%), and pseudoaneurysm in one (2%). Three patients (5%) needed amputation.

CONCLUSION

In situ aortic reconstruction with CAA in infected fields carries a high mortality rate, but most deaths are not the result of allograft failure. However, CAA infection and lethal hemorrhage caused by graft rupture occurs and is concerning. Early reinfection was not reported. Late graft-related complications, such as reinfection, thrombosis, or aneurysmal changes, are unknown. Preliminary data from this registry fail to justify the preferential use of CAA for PGI, MA, or AEE. A multicenter, randomized study is needed to compare results with established techniques.

Long-term outcome after treatment of aortic graft infection with staged extra-anatomic bypass grafting and aortic graft removal

OBJECTIVE

The purpose of this study was to determine long-term outcome in patients with infected prosthetic aortic grafts who were treated with extra-anatomic bypass grafting and aortic graft removal.

METHODS

Between January 1989 and July 1999, 36 patients were treated for aortic graft infection with extra-anatomic bypass grafting and aortic graft removal. Extra-anatomic bypass graft types were axillofemoral femoral (5), axillofemoral (26; bilateral in 20), axillopopliteal (3; bilateral in 1) and axillofemoral/axillopopliteal (2). The mean follow-up was 32.3 +/- 4. 8 months.

RESULTS

Four patients (11%) died in the postoperative period, and two patients died during follow-up as a direct consequence of extra-anatomic bypass grafting and aortic graft removal (one died 7 months after extra-anatomic bypass graft failure, one died 36 months after aortic stump disruption). One additional patient died 72 months after failure of a subsequent aortic reconstruction, so that the overall treatment-related mortality was 19%, whereas overall survival by means of life table analysis was 56% at 5 years. No amputations were required in the postoperative period, but four patients (11%) required amputation during follow-up. Twelve patients (35%) had extra-anatomic bypass graft failure during follow-up, and six patients underwent secondary aortic reconstruction (thoracobifemoral [2], iliofemoral [2], femorofemoral [2]). However, with the exclusion of patients undergoing axillopopliteal grafts (primary patency 0% at 7 months), only seven patients (25%) had extra-anatomic bypass graft failure, and only two patients required amputation (one after extra-anatomic bypass graft removal for infection, one after failure of a secondary aortic reconstruction). Furthermore, primary and secondary patency rates by means of life table analysis were 75% and 100% at 41 months for axillofemoral femoral grafts and 64% and 100% at 60 months for axillofemoral grafts. Only one patient required extra-anatomic bypass graft removal for recurrent infection, and only one late aortic stump disruption occurred.

CONCLUSIONS

Staged extra-anatomic bypass grafting (with axillofemoral bypass graft) and aortic graft removal for treatment of aortic graft infection are associated with acceptable early and long-term outcomes and should remain a primary approach in selected patients with this grave problem.

Surfactant polymers designed to suppress bacterial (Staphylococcus epidermidis) adhesion on biomaterials

We describe a series of surfactant polymers designed as surface-modifying agents for the suppression of bacterial adhesion on biomaterials. The surfactant polymers consist of a poly(vinyl amine) backbone with hydrophilic poly(ethylene oxide) (PEO) and hydrophobic hexanal (Hex) side chains (PVAm/PEO:Hex). Surface modification is accomplished by simple dip coating from aqueous solution, from which surfactant polymers undergo spontaneous surface-induced assembly on hydrophobic biomaterials. The stability of PVAm/PEO:Hex on pyrolytic graphite (HOPG) and polyethylene (PE) was demonstrated by the absence of detectable desorption under flow conditions of pure water over a 24-h period. PEO surfactant polymers with four different PEO:Hex ratios (1:1.4, 1:2.5, 1:4.6, and 1:10.7) and a dextran surfactant polymer were compared with respect to S. epidermidis adhesion under dynamic flow conditions. Suppression of S. epidermidis adhesion was achieved for all modified surfaces over the shear range 0-15 dyn/cm(2). The effectiveness depended on the surfactant polymer composition such that S. epidermidis adhesion to modified surfaces decreased significantly with increasing PEO packing density. Modified HOPG was more effective in reducing bacterial adhesion compared with the corresponding modification on PE, which we attribute to the presence of defects in surfactant polymer assembly on PE. Our results are discussed from the perspective of critical factors, such as optimal PEO packing density and hydration thickness, that contribute to the effectiveness of surfactant polymers to shield a biomaterial from adhesive bacterial interactions.

Oral health of patients scheduled for elective abdominal aortic correction with prosthesis

OBJECTIVE

to evaluate the frequency of potential oral foci of infection in patients scheduled for elective abdominal aortic surgery.

DESIGN

prospective clinical study.

MATERIALS

oral health and dentures of 50 patients (33 males and 17 females, mean age 65 years) were examined before aortic surgery.

CHIEF OUTCOME MEASURES

radiographic and clinical examination with special emphasis on identifying acute and chronic oral and ontogenic conditions which may contribute to aortic prosthesis infection.

RESULTS

eighty-two per cent of the patients had some oral infection foci. The mean number of remaining teeth in the cohort was 9.3, and 21% of these were potential infectious foci (62% in the patients). Twenty-six per cent of the patients suffered from oral Candida infection. Seventy-four per cent of the patients had total or partial dentures, 45% of which were ill-fitting and needed repair.

CONCLUSIONS

oral infectious foci occur frequently in patients needing aortic surgery. Untreated foci may contribute to aortic prosthesis infection. Preoperative oral evaluation and elimination of intraoral infection is recommended for patients scheduled for abdominal aortic repair.

Management of Patients with Prosthetic Vascular Graft Infection

Management of patients with infected prosthetic vascular grafts is one of the most difficult challenges faced by the vascular surgeon. Patients often present with nonspecific symptoms, but delay in treatment can lead to life-threatening sepsis and/or hemorrhage. Fortunately, prosthetic vascular graft infection is uncommon, with the incidence varying between 1 and 6 per cent, depending on the location of the graft. Initially, the potentially infected vascular graft should be imaged using either CT or magnetic resonance imaging, with radionuclide studies being reserved for those instances in which imaging studies do not confirm or exclude the diagnosis of infection. Current treatments for prosthetic vascular graft infection include attempted graft preservation, graft removal with in situ graft replacement (using autogenous or new prosthetic grafts), and graft removal with extra-anatomic bypass. Morbidity and mortality associated with treatment, likelihood of long-term limb salvage, and likelihood of persistent or recurrent infection vary among these types of treatment. Therefore, in an individual patient with a prosthetic vascular graft infection, many things must be considered to appropriately determine the treatment most likely to achieve eradication of the infection and long-term limb salvage with the lowest risk. Regardless, with appropriate application of the techniques currently available for treatment of prosthetic vascular graft infection, long-term elimination of infection and limb preservation can be achieved in the great majority of patients with this grave problem.

The results of in situ prosthetic replacement for infected aortic grafts

BACKGROUND

Treatment of aortic graft infection with graft excision and axillofemoral bypass may carry an increased risk of limb loss, aortic stump blowout, and pelvic ischemia. A review of patients with aortic graft infection treated with in situ prosthetic graft replacement was undertaken to determine if mortality, limb loss, and reinfection rates were improved with this technique.

METHODS

The clinical data of 25 patients, 19 males and 6 females, with a mean age of 68 years (range 35 to 83), with aortic graft infection, treated between January 1, 1989, and December 31, 1998, by in situ prosthetic graft replacement were reviewed. Follow-up was complete in the 23 surviving patients and averaged 36 months (range 4 to 103).

RESULTS

Twenty aortofemoral, 3 aortoiliac, and 2 straight aortic graft infections were treated with excision and in situ replacement with standard polyester grafts in 16 patients (64%), or with rifampin-soaked collagen or gelatin-impregnated polyester grafts in 9 patients (36%). Fifteen patients (60%) had aortic graft enteric fistulas, 8 patients (32%) had abscesses or draining sinuses, and 2 patients (8%) had bacterial biofilm infections. Thirty-day mortality was 8% (2 of 25). There were no early graft occlusions or amputations. There was one late graft occlusion. There were no late amputations. The reinfection rate was 22% (5 grafts). All reinfections occurred in patients operated upon for occlusive disease. Only one reinfection occurred in the rifampin-soaked graft group (11% versus 29%, P = NS). Reinfection tended to be lower in patients with aortoenteric fistulas and without abscess. Autogenous tissue coverage provided statistically significant protection against reinfection. There were no late deaths related to in situ graft infection.

CONCLUSIONS

Patients treated with in situ graft replacement had an 8% mortality and 100% limb salvage rate. Reinfection rates were similar to those of extra-anatomic bypass, but a trend of lower reinfection rates with rifampin-impregnated grafts was apparent. Patients with aortoenteric fistula and without abscess appear to be well treated by the technique of in situ prosthetic grafting and autogenous tissue coverage.

Influence of patient characteristics and treatment options on outcome of patients with prosthetic aortic graft infection

This study was undertaken to determine the influence of patient characteristics and treatment options on survival and limb loss after treatment of prosthetic aortic graft infection. Fifty-three patients treated for prosthetic aortic graft infection were reviewed. Twenty-three presented with groin infection, 12 with sepsis, 10 with aortoenteric fistula, 4 with limb ischemia, and 4 with pseudoaneurysm. Treatment included staged extraanatomic bypass (EAB) plus graft excision in 23 patients, simultaneous EAB and graft excision in 18, in situ graft replacement in 5, and local therapy only in 7. Axillofemoral bypass was done for revascularization in 53 limbs and axillopopliteal bypass in 16 limbs. The results of this study showed that morbidity and mortality of prosthetic aortic graft infection is influenced by the presentation and type of treatment of the infected graft. Staged axillofemoral bypass (when possible) plus graft excision appears to be associated with acceptable outcome (survival with limb salvage in 74%).

Management of infected aortic grafts: development of less invasive surgery using cryopreserved homografts

BACKGROUND

Aortic graft infection is associated with significant mortality and morbidity. Total graft replacement with homografts provides an effective treatment. Partial graft replacement at the site of infection may simplify the surgical procedure.

METHODS

Between January 1991 and December 1996, homografts were used in 18 patients (mean age, 61+/-12 years; range 41-85) with thoracic (4/18; 22%) or abdominal (14/18; 78%) aortic graft infection. Sepsis was present in 14 patients (78%); 6 (33%) had various aortic fistulae. Total graft replacement using homografts was performed in 14 (78%), and partial graft replacement at the site of infection in 4 patients (22%).

RESULTS

Hospital mortality was 11%. During the follow-up period of 22+/-15 months (range, 12-65) there was 1 infection and 1 homograft-related late death after complete homograft replacement, and 1 percutaneous vascular stent placement after partial graft replacement. No other instances of reinfection, suture line rupture or anastomotic aneurysms were observed.

CONCLUSION

Total graft replacement with homografts provides an effective treatment for infected aortic grafts. Partial graft replacement at the site of infection is feasible and safe.

Cryopreserved arterial allografts in the treatment of major vascular infection: a comparison with conventional surgical techniques

OBJECTIVE

Recent findings with cryopreserved heart valve allografts in the treatment of infectious endocarditis suggest that the use of cryopreserved arterial allografts may improve the outcome in patients with vascular infections.

METHODS

Seventy-two patients with mycotic aneurysms (n = 29) or infected vascular prostheses (n = 43) of the thoracic (n = 26) or abdominal aorta (n = 46) were treated with in situ repair and extra-anatomic reconstruction using prosthetic material (n = 38) or implantation of a cryopreserved arterial allograft (n = 34). Disease-related survival and survival free of reoperation were assessed. Morbidity, cumulative lengths of intensive care, hospitalization, antibiotic treatment, and costs were calculated per year of follow-up.

RESULTS

The use of cryopreserved arterial allografts was superior to conventional surgery in terms of disease-related survival (P =.008), disease-related survival free of reoperation (P =.0001), duration of intensive care per year of follow-up (median 1 vs 11 days; range 1 to 42 vs 2 to 120 days; P =.001), hospitalization (14 vs 30 days; range 7 to 150 vs 15 to 240 days; P =.002), duration of postoperative antibiotic therapy (21 vs 40 days; range 21 to 90 vs 60 to 365 days; P =.002), incidence of complications (24% vs 63%; P =.005), and elimination of infection (91% vs 53%; P =.001). In addition, costs were 40% lower in the group treated by allografts (P =.005).

CONCLUSIONS

The use of cryopreserved arterial allografts is a more effective treatment for mycotic aneurysms and infected vascular prostheses than conventional surgical techniques.