Vascular prosthetic graft infection: epidemiology, bacteriology, pathogenesis and treatment

Vascular graft infections and role of PET/CT in patients with persistent bacteraemia

Prosthetic vascular graft infection although a rare complication of vascular reconstruction surgery; has been associated with significant morbidity and mortality. The author presents two patients with prosthetic aortic graft presenting as fever and methicillin sensitive Staphylococcus aureus bacteraemia without any other localising sign of infection. Both patients had a history of postoperative wound infection after their graft placement. Patients remained persistently bacteraemic on appropriate antimicrobial therapy making the clinician suspicious of a vascular graft infection. A [18 F] fluoro-2-deoxy-d glucose positron emission tomography associated to CT scan was used to identify the prosthetic vascular graft infection and since both patients were high-risk surgical candidates, a conservative medical approach was used. They were treated with 6 weeks of nafcillin and rifampin, followed by long-term doxycycline for suppression. This highlights the importance of considering vascular graft infection in patients with recurrent and persistent bacteraemia despite adequate therapy.

Intra-abdominal aortic graft infection: prognostic factors associated with in-hospital mortality

BACKGROUND

Mortality associated with aortic graft infection is considerable. The gold standard for surgical treatment remains explantation of the graft. However, prognostic factors associated with early mortality due to this surgical procedure are not well-known.

METHODS

Retrospective analysis of patients admitted in our center between January 2006 and October 2011 for aortic graft infection. The primary endpoint was in-hospital mortality. A bivariate analysis of characteristics of patients associated with in-hospital outcome was performed.

RESULTS

Twenty five evaluable patients were studied. All patients were male. Their mean age was 67 ± 8.4 years. Most of them (92%) had severe underlying diseases. An in situ prosthetic graft replacement, mainly using cryopreserved arterial allografts, was performed in all patients, excepted one who underwent extra-anatomic bypass. Causative organisms were identified in 23 patients (92%). The in-hospital mortality rate was 48%. Among pre-operative characteristics, age ≥ 70 years, creatinine ≥ 12 mg/L and C reactive protein ≥ 50 mg/L were significantly associated with in-hospital mortality. Hospital mortality rates increased with the number of risk factor present on ICU admission, and were 0%, 14.3%, 85.7% and 100% for 0, 1, 2 and 3 factors, respectively. The only intra-operative factor associated with prognosis was an associated intestinal procedure due to aorto-enteric fistula. SAPS II, SOFA score and occurrence of medical or surgical complications were postoperative characteristics associated with in-hospital mortality.

CONCLUSION

Morbidity and mortality associated with surgical approach of aortic graft infections are considerable. Age and values of creatinine and C Reactive protein on hospital admission appear as the most important determinant of in hospital mortality. They could be taken into account for guiding the surgical strategy.

Endovascular aortoiliac reconstruction to allow excision of an infected axillobifemoral bypass

Axillofemoral graft reconstructions were initially intended to restore lower extremity perfusion in high-risk patients with symptomatic aortoiliac atherosclerotic occlusive disease. However, these reconstructions are now relegated to "bailout" procedures for infected grafts or high-risk critical limb ischemia patients that fail endovascular therapy. Infection of an extra-anatomic bypass graft is a challenging complication as it occurs in poor operative candidates with limited revascularization options and failure has a high rate of amputation and mortality. Described is a novel approach using endovascular reconstruction to treat symptomatic Trans-Atlantic Inter-Society Consensus-II type D aortoiliac lesions allowing for complete excision of an infected axillobifemoral bypass.

Laminar flow reduces cases of surgical site infections in vascular patients

Introduction

Numerous strategies are employed routinely in an effort to lower rates of surgical site infections (SSIs). A laminar flow theatre environment is generally used during orthopaedic surgery to reduce rates of SSIs. Its role in vascular surgery, especially when arterial bypass grafts are used, is unknown.

Methods

A retrospective review of a prospectively maintained database was undertaken for all vascular procedures performed by a single consultant over a one-year period. Cases were performed, via random allocation, in either a laminar or non-laminar flow theatre environment. Demographic data, operative data and evidence of postoperative SSIs were noted. A separate subgroup analysis was undertaken for patients requiring an arterial bypass graft. Univariate and multivariate logistical regression was undertaken to identify significant factors associated with SSIs.

Results

Overall, 170 procedures were analysed. Presence of a groin incision, insertion of an arterial graft and a non-laminar flow theatre were shown to be predictive of SSIs in this cohort. In the subgroup receiving arterial grafts, only a non-laminar flow theatre environment was shown to be predictive of an SSI.

Conclusions

This study suggests that laminar flow may reduce incidences of SSI, especially in the subgroup of patients receiving arterial grafts.

Late infra-renal aortic graft infection: a fearsome complication

Since the 1950s, aortic graft infections (AGIs) constitute one of the most feared complications after reconstructive vascular surgery. This complication is not frequent, ranging from 1% to 2% in the recently reported series; however, the high rate of death and morbidity after therapeutic attempts justifies its dreadful fame. The majority of cases occur during the first month after surgery. Staphylococcus aureus is the cause of 70% of the early infection cases. Late infections, on the other hand, are even rarer, showing a strong relationship with low virulence microorganisms, where Staphylococcus epidermidis is the main cause. Gram-negative bacteria are also observed in late infections, mainly when an aortic or graft enteric fistula is present. Treatment modalities are plenty, but still debatable. The authors report a case of a woman who was operated on 6 years ago for a reconstructive aortic aneurysm with the implantation of an infrarenal Dacron graft in the aorto bifemoral position. She looked for medical assistance with a 2-month history of weight loss, abdominal/back pain, and fever. Her clinical status rapidly deteriorated. A computed tomography of the abdomen disclosed the diagnosis of an AGI. The patient was promptly treated with antibiotics. Surgery was undertaken to explant the infected graft and another graft was placed into the axillobifemoral position. Culture from the infections site was negative. After surgery the patient quickly developed refractory septic shock and died immediately post-operatively.

Aortic prosthetic graft infection accompanied with esophagomediastinal fistulas: A case report

Prosthetic graft infection is difficult to diagnose early, and hence, is associated with high mortality and morbidity rates. A 63-year-old man who had undergone surgical prosthetic replacement for an inflammatory thoracic aortic aneurysm 10 months previously visited our emergency room, complaining of chills, shivering, frequent vomiting, and back pain. He was diagnosed with severe sepsis, and a blood culture detected Streptococcus anginosus and Prevotella oralis. Repeated contrast-enhanced computed tomography (CT) scans of his chest revealed ectopic gas around the graft, and esophagogastroduodenoscopy revealed esophageal perforations at several sites. We therefore diagnosed him with aortic prosthetic graft infection accompanied with esophagomediastinal fistulas. He received medical treatment and three operations and recovered from the infection. This is a rare case of aortic prosthetic graft infection accompanied with esophagomediastinal fistulas, and we conclude that repeated CT is useful for identifying the primary infection site and invasion route in patients with suspected aortic prosthetic graft infection.

A silver nanocomposite biomaterial for blood-contacting implants

Cardiovascular implants must resist infection and thrombosis. A nanocomposite polymeric material [polyhedral-oligomeric-silsesquioxane-poly(carbonate-urea)urethane; POSS-PCU] demonstrates ideal properties for cardiovascular applications. Silver nanoparticles or nanosilver (NS) are recognized for efficient antibacterial properties. This study aims to determine the influence of NS integrated POSS-PCU on thrombogenicity. Silver nitrate was reduced with dimethylformamide and stabilized by the inclusion of fumed silica nanoparticles to prevent aggregation of NS and were incorporated into POSS-PCU to form a range of POSS-PCU-NS concentrations (by weight); 0.20% (NS16), 0.40% (NS32), 0.75% (NS64), and 1.50% (NS128). Surface wettability was determined with sessile-drop water contact angles. Platelets were introduced onto test samples and Alamar Blue (AB), mitochondrial-activity assay, quantified the degree of platelet adhesion whilst platelet-factor-4 (PF4) ELISA quantified the degree of platelet activation. Thromboelastography (TEG) determined the profiles of whole blood kinetics while hemolysis assay demonstrated the degree of blood compatibility. Increasing levels of NS induced greater hydrophilicity. A concentration dependant decrease in platelet adhesion and activation was observed with AB and PF4 readings, respectively. TEG demonstrated that the antithrombogenic properties of POSS-PCU were retained with POSS-PCU-NS16, and enhanced with POSS-PCU-NS32, but was reduced with POSS-PCU-NS64 and POSS-PCU-NS128. POSS-PCU-NS64 and POSS-PCU-NS128 demonstrated a hemolytic tendency, but no hemolysis was observed with POSS-PCU-NS16 and POSS-PCU-NS32. Overall, POSS-PCU-NS32 rendered potent antithrombogenic properties.

Nanomaterial-based treatments for medical device-associated infections

Bacterial infections remain one of the biggest concerns to our society. Conventional antibiotic treatments showed little effect on the increasing number of antibiotic-resistant bacteria. Advances in synthetic chemistry and nanotechnology have resulted in a new class of nanometer-scale materials with distinguished properties and great potential to be an alternative for antibiotics. In this Minireview, we address the current situation of medical-device-associated infections and the emerging opportunities for antibacterial nanomaterials in preventing these complications. Several important antimicrobial nanomaterials emergent from advances in synthesis chemistry are introduced and their bactericidal mechanisms are analyzed. In addition, concerns regarding the biocompatibility of such materials are also addressed.

Hybrid aortoiliac revascularization to avoid nonautogenous groin reconstruction in an intravenous drug abuser

Traditional methods for revascularization of an occluded aortoiliac system have necessitated either in-line aortic reconstruction through an aortobifemoral bypass or extra-anatomic bypass. However, both these approaches require artificial material to be placed in the groin. The consequence of groin infection can be devastating leading to high rates of both limb loss and mortality. One of the most feared patient populations presenting with groin complications is that of the intravenous drug abuser. We present the case of a patient with a long history of intravenous drug abuse with severe aortoiliac disease. Instead of resorting to a more traditional open surgical approach necessitating artificial reconstruction in the groin, we chose to proceed with a hybrid open and endovascular procedure through a direct open surgical access to the aortic bifurcation. This allowed for revascularization without the placement of artificial material in the groin.

In vivo detection of Staphylococcus aureus in biofilm on vascular prostheses using non-invasive biophotonic imaging

OBJECTIVES

Biophotonic imaging was compared to standard enumeration method both for counting Staphylococcus aureus in biofilm and bacterial susceptibility tests of different graft materials.

DESIGN

Prospective, randomized, controlled animal study.

MATERIAL AND METHODS

Five types of vascular grafts were placed subcutaneously in 35 mice and challenged with bioluminescent S. aureus. The mice were divided into equal groups as follows: group A (polyester), group B (polytetrafluoroethylene), group C and D (two types of silver acetate-coated polyester) and group E (bovine pericardium). Controls were given only the bacteria. The bioluminescence signal of S. aureus, able to predict number of viable bacteria in biofilm without any manipulation, was measured at different time points. Five days postinfection, regular cultures of adherent bacteria on grafts were obtained. Comparative analyses between bioluminescence activity and culture enumeration were performed.

RESULTS

The number of viable bacteria on silver-coated prostheses was the slightest, indicating superior bacterial resistance. The density of bacteria on polytetrafluoroethylene and polyester was comparable, with a non-significant advantage for polytetrafluoroethylene. Moreover, bioluminescence detected the number of viable S. aureus in biofilm more exactly compared to enumeration of bacteria.

CONCLUSION

Bioluminescence imaging can be considered a useful tool to characterize susceptibility of any graft material to bacterial biofilm prior to implantation.

[Isolated abdominal pain revealing a paraprosthetic fistula in a patient with Takayasu arteritis]

Aortic aneurysms and stenosis occurring in Takayasu arteritis may require aortic prosthesis that can be complicated by aorto-digestive fistula. We report a 41-year-old female who presented with an isolated abdominal pain revealing a para-prosthetic aorto-duodenal fistula complicating a Takayasu arteritis. The diagnosis of aorto-digestive fistula may be difficult if abdominal pain is isolated and imaging inconclusive. Surgical procedure may be necessary to obtain the diagnosis and constitutes the main part of the treatment before fatal outcome.

Microbial Spectrum and Primary Resistance to Rifampicin in Infectious Complications in Vascular Surgery: Limits to the Use of Rifampicin-Bonded Prosthetic Grafts

There are reports that rifampicin-bonded prosthetic grafts might be a suitable alternative to autologous grafts in vascular graft infections and infectious vascular complications. We characterize the spectrum of microbial agents and susceptibility to antibiotic treatment, especially to rifampicin, in these patients. We carried out a retrospective analysis of wound-swaps and blood cultures in 48 patients with infected prosthetic vascular grafts or primary infectious vascular complications. In 15 of 48 patients (31%), the analysis showed that the microbial organism causing the infection was resistant or not susceptible to rifampicin. Rifampicin-bonded prosthetic grafts should be used with caution in acute infectious complications in vascular surgery, because in about 30% of the cases, the initiating microbial organisms are resistant or not susceptible to rifampicin. Without preoperative confirmation of susceptibility to rifampicin, autologous reconstruction should be preferred.

ECM-based materials in cardiovascular applications: Inherent healing potential and augmentation of native regenerative processes

The in vivo healing process of vascular grafts involves the interaction of many contributing factors. The ability of vascular grafts to provide an environment which allows successful accomplishment of this process is extremely difficult. Poor endothelisation, inflammation, infection, occlusion, thrombosis, hyperplasia and pseudoaneurysms are common issues with synthetic grafts in vivo. Advanced materials composed of decellularised extracellular matrices (ECM) have been shown to promote the healing process via modulation of the host immune response, resistance to bacterial infections, allowing re-innervation and reestablishing homeostasis in the healing region. The physiological balance within the newly developed vascular tissue is maintained via the recreation of correct biorheology and mechanotransduction factors including host immune response, infection control, homing and the attraction of progenitor cells and infiltration by host tissue. Here, we review the progress in this tissue engineering approach, the enhancement potential of ECM materials and future prospects to reach the clinical environment.

Coverage Strategies in Exposed Implants

Implants are widely used and are not without complications. The most serious complication is infection with consequent exposure of the implant and is characterized by increased morbidity and mortality. Until recently, infected implants were removed and replaced with another one. These operations are accompanied by increased morbidity and might result in permanent disability. Coverage of the implant with a flap is an alternative solution. The objective of this article is to study the effectiveness of muscle or myocutaneous flaps in covering infected and exposed implants. A series of 17 patients with infected implants, which were treated with coverage of the implant with muscle or myocutaneous flap, is presented. Eight patients had an orthopedic implant, seven a vascular implant, and two had a pacemaker. The flaps ensured immediate coverage of the implant and the biologic ability of eliminating the infectious process with the increased concentration of antibiotics resulting from increased blood flow of the muscle. In all the patients, the implants were preserved and the infectious process was eliminated. The use of muscle and myocutaneous flaps in the treatment of infected implants is therefore effective and in some cases it is superior to other methods because of lower morbidity and cost.

Uruguayan experience with cryopreserved arterial homografts

INTRODUCTION

We analyzed the Uruguayan experience with cryopreserved arterial homografts. We studied 55 medical records in the period from June 9, 2000 to April 7, 2007, including 41 from males and 14 from females, ranging from 36-78 years of age. The clinical indications were as follows: Group 1, revascularization of infrainguinal atherosclerotic occlusive disease by bypass due to the lack of availability of a suitable vein (n = 35); Group 2, substitution of an infected prosthetic grafts (n = 15); and Group 3, arteriovenous fistula (AVF) after failure of previous prosthetic loops by repeated thrombosis and/or infection in the absence of a vein (n = 5).

RESULTS

Among Group 1, primary and secondary patency rates were 61% and 71%, respectively at 1 year with 15 complications, 3 infections, 8 thromboses, 2 aneurysms, 1 homograft degradation, and 1 death related to surgery. Among Group 2, the primary and secondary patency rates were 71% and 79%, respectively, at 1 year with 6 patients experiencing complications. Group 3 did not have complications with a primary patency rate of 67% at 1 year.

CONCLUSIONS

The use of cryopreserved arterial homografts is a valid, accessible, and safe alternative in complicated vascular situations. In our country, it is a technology to consider for patients with critical limb ischemia, when the risk of a major amputation is high and it is not possible to have a suitable vein or prosthetic bypass. It can be an excellent alternative for the substitution of infected synthetic bypasses, especially to substitute in situ for an infected aortic graft.

Vascular prostheses with covalently bound gentamicin and amikacin reveal superior antibacterial properties than silver-impregnated ones--an in vitro study

OBJECTIVE

This study aims to compare the antibacterial activities of vascular prostheses: silver-impregnated and modified with covalently immobilised antibiotics.

MATERIALS AND METHODS

Six types of protein-sealed vascular prostheses were modified with amikacin and gentamicin according to the method described in the Polish Patent Office. Their antimicrobial properties were estimated against 14 reference and clinical strains and compared with those of InterGard Silver grafts. Cytotoxicity of the tested grafts was estimated against human skin fibroblasts.

RESULTS

Prostheses modified with antibiotics in a stable covalent mode were found to be much more effective against bacterial growth and biofilm formation, as well as in case of methicillin-resistant Staphylococcus aureus (MRSA), than InterGard Silver. They inhibited the bacterial growth for at least 30 days, without losing higher than 10% of the initial amount of its drug content. They were also good, non-toxic matrices for growth of human skin fibroblasts.

CONCLUSIONS

Prostheses modified with covalently immobilised antibiotic according to our technique are much more effective than InterGard Silver at protection against bacterial growth. They are also compatible with human skin fibroblasts.

CORRESPONDENCE

The practice of defensive medicine has reached new heights, thanks largely to the rising number of medical malpractice lawsuits. While every department in the hospital is affected by this practice, radiological departments seem to be the worst hit (Baicker et al, 2007).

Secondary iliac-enteric fistula to the sigmoid colon complicated with entero-grafto-cutaneous fistula

We report the case of a 67-year-old man who was admitted to our department with acute rectal bleeding. The patient had had previous aortoiliac surgery with the utilization of an aortobifemoral vascular prosthesis. Diagnosis of aortoenteric fistula was made between the distal suture line of the right graft leg and the sigmoid colon. This fistula had an enterocutaneous component. After exploratory laparotomy, primary resection of the sigmoid colon, exstirpation of the enterocutaneous fistula, excision of the right graft leg and extraanatomical crossover bypass were successfully performed. This study reports a rare type of aorto/ilac-enteric fistula to the left colon complicated with an entero-grafto-cutaneous component and describes an unusual and successful surgical treatment method.

Less-invasive and highly effective method for preventing methicillin-resistant Staphylococcus aureus graft infection by local sustained release of vancomycin

OBJECTIVE

Methicillin-resistant Staphylococcus aureus graft infection is one of the most serious complications of vascular surgery. Vancomycin is a potent antibiotic against methicillin-resistant S. aureus; however, systemic administration of vancomycin is not very effective against methicillin-resistant S. aureus graft infection. Therefore, we investigated whether a local sustained release of vancomycin prevents methicillin-resistant S. aureus graft infection.

METHODS

We have developed a poly-L-lactide-co-caprolactone sheet that enabled sustained release of vancomycin for 2 weeks. An expanded polytetrafluoroethylene vascular graft patch (1.5 mm2) was sutured at the anterior wall of the incised murine abdominal aorta. Methicillin-resistant S. aureus (1.0 x 10(3) colony-forming units) was inoculated onto the graft surface. Thereafter, the graft was treated as follows (n = 6 each): no treatment (control group), local injection of an aqueous solution of vancomycin (vancomycin solution group) and local implantation of poly-L-lactide-co-caprolactone containing vancomycin (vancomycin-PLCA group). After 7 days, the graft and blood were sampled and cultured.

RESULTS

The methicillin-resistant S. aureus counts in the grafts of the vancomycin-PLCA group were significantly lower than those of the other groups. Blood cultures of the vancomycin-PLCA group were all negative, whereas those of the other groups were all positive for infection. The survival rate in the vancomycin-PLCA group at 28 days was considerably higher than that in the control group (83.3% vs 16.7%).

CONCLUSIONS

A local sustained-release sheet containing vancomycin reduced methicillin-resistant S. aureus counts in the infected vascular grafts, prevented sepsis, and drastically improved survival rates. This can be used as a highly effective and less-invasive adjunctive treatment method for preventing prosthetic methicillin-resistant S. aureus graft infection.

Laparoscopic Diagnosis and Treatment of Aortic Vascular Prosthetic Graft Infections in a Porcine Model

OBJECTIVES

To study the feasibility and efficacy of experimental laparoscopy in the diagnosis of aortic graft infection in pigs.

MATERIAL AND METHODS

Eight pigs had an aortic tube graft implanted and inoculated with either 5 x 10(4) or 10(6) CFU of Staphylococcus aureus ATCC 29213. Laparoscopy was performed after a median of 20 days with debridement and sampling for bacterial culture. Thereafter, the grafts were locally soaked in rifampicin and postoperatively, the pigs received rifampicin and ciprofloxacin orally for two weeks and were then sacrificed.

RESULTS

All pigs developed graft infection. One pig died from severe clostridial septicaemia before laparoscopy could be performed. The remaining pigs had all samples for bacterial culture taken by laparoscopy from the inflamed tissue. The temperature dropped significantly after laparoscopy, and no macroscopic signs of infection presented at autopsy. However, only culture from one pig was without S. aureus at autopsy.

CONCLUSIONS

Laparoscopy is a potential diagnostic tool for aortic graft infection and also affords the opportunity to carry out bacteriological sampling and local antibiotic treatment. The efficacy of laparoscopic treatment needs further evaluation.

[Actinomyces odontolyticus isolation during prosthetic aortic graft infection with paraprosthetic duodenal fistula]

INTRODUCTION

Prosthetic vascular graft infection is a rare complication of vascular surgery. We report a case with graft enteric fistula and Actinomyces odontolyticus bacteremia.

EXEGESIS

A 73 year-old man with a prosthetic aortic graft and who had a parodontal disease, has been hospitalised for fever of unknown origin. Blood cultures grew with Escherichia coli and Actinomyces odontolyticus. The imaging studies indicated graft infection. Laparotomy has confirmed the diagnosis and highlighted a polymicrobial infection and a paraprosthetic duodenal fistula. A review of the literature's data concerning prosthetic vascular graft infections is made. The role of Actinomyces odontolyticus in that case is discussed.

CONCLUSION

Prosthetic aortic graft infection due to graft enteric fistula is usually a polymicrobial infection and is a late complication of aortic surgery. Imaging is essential for the diagnosis of prosthetic aortic graft infection. It is possible that Actinomyces odontolyticus has contributed to prosthesis infection in this case.

Contamination and decontamination of Doppler probes

INTRODUCTION

Nosocomial infection occurs in 2-9% of patients undergoing vascular surgery and can lead to death, amputation or require complex revision surgery. Neck ties, pagers, stethoscopes and Doppler probes have been shown to carry pathogens. We measured bacterial colonisation of Doppler probes on a vascular unit and audited the effect of staff education at reducing this contamination.

MATERIALS AND METHODS

Bacteriological culture swabs were taken from hand-held Doppler probes on the vascular surgical ward and clinic. There was no protocol for cleaning the Doppler probes, so manufacturers were contacted for their recommendations. The results of cultures were presented to nursing and medical staff, who were then asked to clean the probes with alcohol wipes after each use. After an interval of 1 week, bacteriological cultures from the same Doppler probes was repeated.

RESULTS

Fifty bacteriological cultures were performed from 10 Doppler probes over a 4-week period. Thirteen (26%) cultures were positive for diphtheroids, coliforms, coagulase-negative staphylococci and skin flora. After staff education, 42 further swabs were taken from the same probes; two positive cultures were obtained with scanty growth of skin flora (chi2 P < 0.05).

CONCLUSIONS

Staff education and simple cleaning significantly reduces the contamination of hand-held Doppler probes and may help prevent nosocomial infection.

Sustained-release vancomycin sheet may help to prevent prosthetic graft methicillin-resistant Staphylococcus aureus infection

OBJECTIVE

The purpose of this study was to evaluate the effectiveness of a sustained-release sheet with vancomycin (VCM) to prevent prosthetic graft infection.

METHODS

VCM was incorporated into a poly-L-lactide-co-caprolactone (PLCA) sheet (VCM-PLCA). The release profile of VCM from the VCM-PLCA sheet and the tissue concentration of VCM released in vivo were examined. To assess the antibacterial effect of the VCM-PLCA sheet, a sterile Dacron sheet was implanted into 96 male mice (C57BL/6), who were randomly divided into four groups of 24 each and treated as follows: no treatment (group A, control group), a local bolus injection of an aqueous solution of VCM (group B), a plain PLCA sheet (group C), and a VCM-PLCA sheet (group D). After the treatment, methicillin-resistant Staphylococcus aureus (MRSA) (1 x 10(6) colony forming units) was inoculated onto the Dacron graft surface. The Dacron grafts were retrieved on days 3, 7, 10, and 14 after the implantation, and the number of MRSA in the Dacron grafts was counted.

RESULTS

VCM was slowly released from the VCM-PLCA sheet over 2 weeks in vivo, and the mean in vivo concentrations of VCM in the tissue around a VCM-PLCA sheet were 7.95, 26.39, 13.87, 12.51, 8.36, and 10.33 mug/mL (the minimum inhibitory concentration of VCM against MRSA is 2.0 mug/ml), at 1, 2, 5, 7, 10, and 14 days after the implantation, respectively. MRSA colonization on the cultivated agar plates was detected in all samples from groups A, B, and C at any postoperative time points. In contrast, some samples were negative for bacterial cultures in group D (2, 3, 1, and 2 samples out of 6 samples each on days 3, 7, 10, and 14 after the implantation, respectively). At all time points, the number of MRSA bacteria in the implanted Dacron graft in group D was by far the lowest (P < .01 at each time point).

CONCLUSIONS

The sustained-release sheet with VCM appears to be effective for the reduction of subcutaneous prosthetic graft infection.

A systematic review and meta-analysis of treatments for aortic graft infection

OBJECTIVE

We compared pooled estimates of event rates for amputations, conduit failures, reinfections, early mortalities, and late mortalities in patients with aortic graft infection who were treated by extra-anatomic bypass, rifampicin-bonded prostheses, cryopreserved allografts, or autogenous veins.

METHODS

A systematic review was conducted of English language reports in MEDLINE back to 1985 and a meta-analysis was performed on the results. Studies were selected on the basis of medical subject headings aortic, graft, and infection, and also by a standardized and independent quality rating. Inclusion and exclusion criteria were met by 37 clinical studies. Pooled estimates of mean event rates for amputations, conduit failures, reinfections, early (< or =30 day) mortalities, and late (>30 days) mortalities were determined for each treatment modality. Tests of heterogeneity and sensitivity analyses were performed.

RESULTS

Fixed effect analyses, derived after tests of heterogeneity, yielded overall pooled estimates of mean event rates for all outcomes combined of 0.16 for extra-anatomic bypass, 0.07 for rifampicin-bonded prostheses, 0.09 for cryopreserved allografts, and 0.10 for autogenous vein; a lower value signifies fewer overall events associated with the treatment modality. Overall, the robustness of our meta-analysis was demonstrated by the reasonable heterogeneity of pooled data from individual studies (Q statistic <25; P >.1 for all treatment outcomes across all modalities) and the limited variability of outcomes after sensitivity analyses.

CONCLUSION

Although limited by the design of individual published studies whose data were pooled together in this meta-analysis, our results lead to questions concerning whether extra-anatomic bypass should remain the gold standard for treatment of aortic graft infection.

Prosthetic vascular graft infection: A risk factor analysis using a case–control study

OBJECTIVES

Several factors have been anecdotally reported to increase the risk of prosthetic vascular graft infection (PVGI), a serious complication with high mortality and limb amputation rates. The goal of this study is to confirm purported risk factors using a well-designed statistical model.

METHODS

Patients undergoing vascular graft placement at Mayo Clinic Rochester between January 1, 1982 and December 31, 2002 were retrospectively evaluated, excluding redo cases. PVGI cases had to meet one of the following criteria: perigraft air or fluid >8 weeks postoperatively, positive Gram stain or cultures of graft or perigraft material, intraoperative gross purulence, failure of graft incorporation, or exposed graft. Each case had two controls matched for age, gender and date of surgery. Duration of follow-up for a given control had to be at least equal to the time to infection of the corresponding case. Demographic and other clinical data were collected for each patient.

RESULTS

Fifty-one cases and 102 controls met the inclusion criteria. Median age was 68 years. Staphylococcal species were identified in 45% of the total number of cases, and 60% of cases with a recovered organism. Univariate analysis identified groin incision, wound complication and wound infection as significant risk factors for PVGI (p<0.005 for all three factors). After adjusting for age and surgery date, multivariate analysis confirmed the statistical significance of groin incision and wound infection as risk factors for PVGI.

CONCLUSIONS

This is the first published risk factor analysis that includes statistical evaluation in a case-control study of PVGI. Groin incision, wound complication, and wound infection are significantly associated with developing PVGI. These findings will assist in identifying patients at increased risk of developing subsequent infection.

SUMMARY

In order to confirm purported risk factors of prosthetic vascular graft infections (PVGI), a well designed case-control study was conducted at Mayo Clinic, Rochester, MN. Univariate and multivariate analyses of 51 cases and 102 controls identified three statistically significant risk factors for the development of PVGI: groin incision, wound complication, and wound infection.

The Structural and Cellular Viability in Cryopreserved Rabbit Carotid Arteries

OBJECTIVE

We investigated the histological and mechanical changes in addition to viable cellular recovery in cryopreserved blood vessels.

MATERIALS AND METHODS

Rabbit carotids were cryopreserved in a cryoprotective medium containing 1.5 M of 1,2-propanediol (PD) and then were thawed slowly in an ice bag that had been precooled in liquid nitrogen. Fresh carotids were used as the control. The fresh and freeze-thawed arteries were cultured for the growth of vascular smooth muscle cells (VSMCs). The freeze-thawed arterial tissues were perfused in vitro for 6, 12, or 24 h, respectively, to assess the integrity of carotid walls and the mechanical properties.

RESULTS

The results showed that it took almost the same time (24 approximately 36 h) for the VSMCs of the PD-cryopreserved arteries to regenerate as those from the fresh arteries. Their growing speeds also were similar. On the contrary, Me2SO-cryopreserved (1.5 M) arteries were unable to regenerate VSMCs in culture. After freeze-thawing, the mechanical properties decreased significantly (P < 0.003 for elastic modulus and P < 0.001 for fracture strength). After in vitro perfusion of the freeze-thawed carotid arteries, all of the survived endothelial cells fell off, and some of the VSMCs denaturalized or necrosed. The internal elastic fibers and collagen showed various degrees of cracking. The mechanical properties were decreased (P < 0.05).

CONCLUSION

Our findings demonstrate that the PD-containing cryoprotective medium can preserve regenerative capacity of VSMCs, which makes it a useful technique for viable VSMC recovery. However, the freeze-thawing process and the in vitro perfusion caused serious disruption in the arterial mechanical properties, rendering the cryopreserved blood vessels less useful for vessel reconstruction.

Update on the Use of Antibiotics in Cutaneous Surgery

BACKGROUND

Antibiotics are often prescribed in perioperative settings, including dermatologic surgery. Given the continued evolution in the breadth and complexity of cutaneous procedures performed and inevitable localized or distant infections that occasionally occur, it seems prudent to periodically evaluate findings and recommendations from the literature regarding the use of antibiotics in cutaneous surgery.

MATERIALS AND METHODS

Literature review from English-language sources from the past 30 years, especially focusing on sources from the past 5 to 10 years. Data were examined for a variety of cutaneous surgical procedures, routes of antibiotic administration, and consideration of both cutaneous and distant infections.

RESULTS

The literature suggests that, for most routine skin procedures, antibiotic use is probably not warranted for the prevention of surgical wound infection, endocarditis, and late prosthetic joint infections. During prolonged Mohs procedures, delayed repairs, grafts, takedowns of interpolation flaps, or any procedure that breaches a mucosal surface, the evidence is less clear, and decisions should be made on a case-by-case basis. Topical antibiotics are probably overused, although silver sulfadiazine may have an undeserved negative reputation among dermatologists. Systemic prophylactic antibiotics for laser resurfacing and liposuction appear not to be routinely necessary, although patients with known prior herpes infection likely should receive antiviral prophylaxis. The overall reported infection rates and infectious complications remain low in dermatologic surgery, and antibiotic therapy may be prescribed excessively or inappropriately as a result. CONCLUSION.: Antibiotics continue to be widely used, and through varying routes of administration, in the setting of dermatologic surgery. Prudent use of these agents is indicated in high-risk patients, certain anatomic locations, and the presence of overt infection. Additional studies may help clarify the most appropriate indications, and in which patient populations, in the future.

Intra-arterial device infections

As an increasing number and variety of prosthetic devices are used in cardiovascular medicine, novel infectious complications have been described. Infection of intra-arterial devices, including arterial closure devices, prosthetic carotid patches, coronary artery stents and endovascular stents, and stent-grafts, is now being reported. Prosthetic vascular graft infection is an older, more common, and better-characterized entity, but recent developments in the surgical management of these infections have prompted a re-examination of the syndrome. Staphylococcal species account for most intra-arterial device infections, and often, morbidity and mortality rates are high. An update on intra-arterial device infections is warranted.

Cryopreserved arterial allografts for in situ reconstruction of infected arterial vessels

OBJECTIVE

To review our experience of using cryopreserved allografts for in situ reconstruction in the presence of infection involving the aorta, iliac or femoral arteries.

DESIGN

Retrospective clinical study.

METHODS

From 3/2000 to 8/2003 all patients with mycotic aneurysms or secondary infection following earlier prosthetic replacement were treated with cryopreserved human allografts. Forty-two patients, 39 (93%) with a prosthetic graft infection and 3 (7%) with a mycotic aneurysm of the abdominal aorta were treated. Six (14%) had aorto-enteric fistulas, 5 (12%) had ruptured aneurysms, and 2 also had vertebral destruction. The median follow-up time was 20 months (range 1-42 months).

RESULTS

Thirty-day mortality was 14%. Three patients died due to multi-organ failure, two patients died from hypovolaemic shock due to allograft rupture and one from rupture of the native aorta. The overall mortality was 24% (four additional patients). Graft patency was 100% at 30 days and 97% at follow up in the survivors. The mean actuarial survival time was 32 months (95% CI=27-37 months).

CONCLUSIONS

Cryopreserved allografts for the in situ reconstruction of infected arteries or grafts have acceptable intermediate results.