Surgical management of infrainguinal arterial prosthetic graft infections: review of a thirty-five-year experience

Proteomic analysis of Staphylococcus aureus biofilms grown in vitro on mechanical heart valve leaflets

The in vitro colonization of three commercial heart valve leaflets by Staphylococcus aureus was investigated. The leaflets, made of pyrolytic carbon alloyed with or without silicon, displayed similar surface properties (wettability, roughness) and were readily colonized by S. aureus that formed patchy biofilms on the three supports. A proteomic approach was used to assess the physiological status of biofilm populations by comparing their protein maps to those of bacteria cultured as free cells in the presence or absence of biofilm substratum. Principal component analysis (PCA) revealed, for each tested leaflet, statistical relationships between the protein maps of the biofilm and free-floating microbial populations. A spot-by-spot comparison of protein levels on two-dimensional electropherograms showed that many proteins were accumulated or underproduced by microbial populations grown in the presence of a leaflet compared with protein levels in control free populations. The number of accumulated proteins was noticeably higher than that of underproduced polypeptides. This protein overproduction was emphasized in biofilm populations. Several proteins, some of which were identified, were differentially produced by both surface-associated planktonic and biofilm-grown cell populations compared with control free-cell ones cultured in the absence of leaflet, whatever the leaflet tested. The potential of this proteomic approach for fighting against microbial adhesion and biofilm formation is discussed.

Case Study: Chronic Femoropopliteal Prosthetic Graft Infection With Exposed Graft

One of the most feared complications following vascular reconstruction is infection due to the attendant risks of limb loss, sepsis, or death. The reported incidence of infection following infrainguinal prosthetic graft infection is 2.5% with associated mortality rates and amputation rates of 18% and 41%, respectively. There are several options in treating infected prosthetic infrainguinal bypass grafts. Some authors have advocated complete removal of the infected graft with concomitant in situ revascularization using autogenous tissue or extra-anatomic bypass using either autogenous or prosthetic material, depending upon the clinical circumstances. Other authors have advocated attempting graft preservation to decrease the risk of amputation. Infected, thrombosed grafts are generally treated with graft excision alone with care taken to preserve collateral flow. The treatment options may also be influenced by the type of infection, as infections caused by gram-negative bacteria are thought to be more virulent than those associated with gram-positive bacteria. We recently treated a patient with an 18-month history of an exposed prosthetic graft in the groin, which was infected by Proteus mirabilis. Despite the extended period of graft exposure and despite gram-negative bacteria being the causative organism, the patient reported only intermittent drainage of pus from the groin. The management of this unusual infection forms the basis of this report.

Role of negative pressure wound therapy in treating peripheral vascular graft infections

Wound complications involving large subcutaneous vessels can cause significant challenges for surgeons. Negative pressure wound therapy (NPWT) has been increasingly used for treating complex wounds in vascular surgery, including groin infections, either as a bridge to surgical closure or as a primary wound treatment modality. Although a growing body of evidence exists for managing various problematic wounds, such as diabetic foot ulcers and open abdominal wounds, the role of NPWT in wounds involving large blood vessels or wounds complicating infected vascular grafts has not been well defined. A multidisciplinary advisory panel reviewed the literature relevant to wounds related to vascular surgical procedures and complications, focusing on large subcutaneous or infected vascular conduits. The results supported by the literature and the clinical practice of the consensus panel suggested that NPWT can be a useful adjunct to the management of vascular groin infections and dehiscences but must be used with caution.

Evolving Microbiology and Treatment of Extracavitary Prosthetic Graft Infections

The authors report the microbiology and outcomes following an individualized treatment algorithm for extracavitary (EC) prosthetic graft infection, including the use of graft preservation and in situ graft replacement techniques. A retrospective 8-year review of 87 patients treated for EC prosthetic graft infections was carried out. The treatment algorithm included culture-specific antibiotic therapy, surgical site debridement with antibiotic bead placement, selected graft preservation with muscle flap coverage, or graft excision with in situ conduit replacement. Outcomes measured included death, limb loss, and recurrent infection. It was found that present-day management of EC prosthetic graft infections is associated with lower mortality and morbidity despite changes in microbiology and the increased application of graft preservation and in situ grafting treatments.

Prevention of Staphylococcus aureus graft infection by a new gelatin-sealed vascular graft prebonded with antibiotics

OBJECTIVE

The aim of this study was to evaluate the efficacy of a new gelatin-sealed graft prebonded with two antibiotics in resisting infection with Staphylococcus aureus (S aureus) A980142 after direct bacterial application in a dog model.

METHODS

Twelve 6.0-mm polyester grafts were implanted in dogs end-to-end into the infrarenal aorta. The dogs were divided into two groups. A test group (n = 6) received experimental antibiotic-bonded gelatin-sealed knitted polyester grafts, loaded with two antibiotics, rifampin and tobramycin. A control group (n = 6) received commercial gelatin-sealed knitted polyester grafts. At the end of graft implantation, 50 mul of a 1.8 x 10(4) CFU/mL S aureus solution were instilled directly over the graft. One week after implantation, grafts were harvested with sterile technique. Quantitative cultures were obtained from all the harvested grafts. The results were expressed as colony-forming units per cm(2) of surface of the graft. Bacteriological study was also performed on various tissue samples. The chi(2) test was used to compare the culture proven infection of control and antibiotics-bonded grafts.

RESULTS

Mean inoculum size was similar in the two groups of dogs. Five of the six control grafts grew S aureus A980142 at the time of graft removal, whereas none of the six antibiotic-bonded gelatin-sealed grafts were infected (P = .0192). None of the organ samples were infected in the group implanted with antibiotic-bonded grafts, whereas 15/34 samples grew S. aureus in the control group.

CONCLUSION

These results indicate that this gelatin sealed graft prebonded with two antibiotics resists infection caused by S aureus graft contamination in a dog model.

Infección asociada a prótesis vascular: manejo exitoso sin retirada de prótesis

INTRODUCTION

Removal of graft with intravenous antibiotics is traditionally considered the most effective treatment of vascular graft-associated infections. However, an increasing number of reports suggests that this complication can be effectively treated without graft removal.

METHODS

A prospective study to evaluate the outcome of conservative management of vascular graft-associated infection seen in our center was performed. The diagnosis of graft-associated infection was based on microbiological tests, and imaging studies. In our study, patients were hemodynamically stable with functioning vascular graft as per clinical and imaging evaluations. Conservative management included antibiotic treatment and local debridement without removal of vascular graft.

RESULTS

Fourteen patients with vascular graft-associated infection were enrolled in our study. Eleven out of 14 patients (78.6%) responded successfully to conservative management. Treatment failure was reported in 3 patients, 2 of whom required graft removal. After a two-year follow-up, these 14 patients were clinically stable without recurrence of infection.

CONCLUSIONS

Our study has revealed that conservative management of vascular graft-associated infection seems to be effective and should be considered in hemodynamically stable patients with functioning vascular graft.

Managing extracavitary prosthetic vascular graft infections: a pathway to success

Prosthetic vascular graft infections portend grave consequences if not treated expediently. Despite the low incidence of infection, the potential for limb loss or death greatly magnifies this complication. The surgical management of prosthetic graft infections has evolved over the last 2 decades. With the myriad therapeutic options now available, an algorithm is necessary to provide the optimal surgical treatment of Samson groups 1 through 5 extracavitary infected vascular prostheses. An extensive review of the literature was undertaken to evaluate the most effective management schemes. The authors found that 3 factors--Samson classification, bacteriology, and patient vascular anatomy--are vital to the surgical strategy. These 3 criteria were examined, and an algorithm was developed based on successful clinical and experimental results. This review provides a step-by-step rationale for the surgical management of extracavitary prosthetic graft infections according to the most successful reported outcomes.

Does the timing of reoperation influence the risk of graft infection?

OBJECTIVE

This study compared the incidence and characteristics of graft infection in patients who underwent early vs late revisional surgery of lower extremity arterial bypass grafts.

METHODS

Between 1992 and July 2005, 500 revisional procedures were performed on 198 lower extremity bypass grafts. Patients whose revisions were performed <30 days after the primary bypass were in the early revision (ER) group (n = 99), and those done >30 days after bypass were in the late revision (LR) group (n = 99). Infection was defined as cellulitis with graft exposure or purulence in continuity with a graft that required antibiotics and operation for infection control. Mean follow-up was 60 months (range, 2 to 60 months). Groups were compared using Student's t test.

RESULTS

The ER group included 66 autogenous and 33 prosthetic grafts. The LR group consisted of 53 autogenous and 46 prosthetic grafts. Of the 500 revisional procedures performed, 17 graft infections occurred (3.4%). Twelve (70.6%) were prosthetic grafts and five (29.4%) were autogenous grafts (P = .004). Defining the infection rate per graft rather than per revisional procedure, the ER group had a significantly higher graft infection rate at 11% (11/99) compared with 6.1% in the LR group (6/99; P = .012). The risk of infection for prosthetic grafts was significantly higher within the ER group at 27.3% (9/33) compared with autogenous grafts at 3.1% (2/66; P = .0001). Infection developed in three vein grafts and three prosthetic grafts in the LR group (P = NS). For prosthetic graft revisions only, infection risk was 27.3% (9/33) in the ER group and 6.5% (3/46) in the LR group (P = .005). The most common cultured pathogen was methicillin resistant Staphylococcus aureus (ER, 6/11 vs LR, 3/6; P = NS). Within the ER group, the prevalence of Pseudomonas aeruginosa was significantly higher at 27.3% (3/11) compared with 0% (0/6) in the LR group (P = .04).

CONCLUSIONS

Early revision of lower extremity arterial bypass grafts has a significantly higher risk of graft infection compared with revision >1 month after surgery. Infection will develop in approximately 25% (9/33) of prosthetic grafts that are reoperated on early. If feasible, reoperation should be delayed >1 month for prosthetic grafts needing revision. Endovascular or extra-anatomic interventions should be considered if early revision is mandated in this group.

Use of antibiotic-loaded polymethylmethacrylate beads for the treatment of extracavitary prosthetic vascular graft infections

PURPOSE

This study was conducted to assess the efficacy of antibiotic-loaded polymethylmethacrylate (PMMA) beads in the management of lower extremity extracavitary prosthetic arterial graft infection.

METHODS

This was a retrospective review of 34 patients treated for vascular surgical site (VSS) infections involving 36 prosthetic lower extremity arterial bypasses using antibiotic-loaded PMMA beads and culture-specific parenteral antibiotics for 4 to 6 weeks. Sites of graft infection were explored, debrided, and cultured. As determined from the results of Gram's stains of VSS purulence, PMMA powder was polymerized with an antibiotic (vancomycin, daptomycin, or tobramycin/gentamicin, or a combination), molded into a chain of beads, and implanted adjacent to the infected graft after debridement and pulsed-spray antibacterial lavage. All wounds were closed primarily with planned exploration to verify sterilization before a graft preservation or in situ replacement procedure. Treatment outcomes, including wound sterilization, were analyzed based on tissue culture isolates, procedures for persistent infection, and freedom from graft infection.

RESULTS

Cultures isolated 42 pathogens, (32 gram-positive, 9 gram-negative, 1 Candida albicans) with methicillin-resistant Staphylococcus aureus (MRSA) cultured from 16 (44%) of 36 surgical site infections. As determined from the initial operative Gram's stain or a prior culture result, vancomycin PMMA beads were implanted in 29 of 36 VSS infections at the first procedure; daptomycin (n = 4) or tobramycin (n = 3) beads were implanted in the rest. Repeat VSS exploration and culture results led to an average of 2.5 antibiotic bead replacements before definitive treatment. A sterile (no growth on tissue culture) VSS was achieved in 87% of cases before a graft preservation (n = 16) or in-situ replacement of an infected graft (n = 20) procedure. No patient deaths occurred. Early and late limb salvage was 100%. Infection recurred in 4 (11%) VSSs during a mean 23-month follow-up period, one within 3 months owing to unrecognized bowel injury associated with in situ replacement of an aortofemoral graft limb.

CONCLUSION

Antibiotic-loaded PMMA beads may be a useful adjunct in the contemporary surgical management of VSS infection involving a prosthetic graft. Wound sterilization was achieved in most VSSs before graft preservation or an in-situ replacement procedure, including infections caused by MRSA, a pathogen isolated in half of the extracavitary prosthetic graft infections. This preliminary trial shows the potential benefit of this new technique, but further study is required to prove efficacy.

Early post-operative glucose levels are an independent risk factor for infection after peripheral vascular surgery. A retrospective study

OBJECTIVE

To evaluate whether hyperglycaemia in the first 48 h after infrainguinal vascular surgery is a risk factor for post-operative infection, independent from factors associated with insulin resistance and surgical stress.

DESIGN

Retrospective cohort study.

PATIENTS AND METHODS

Patients who underwent infrainguinal vascular surgery in our hospital between March 1998 and March 2003 were included. Glucose values until 48 h after surgery were retrieved from laboratory reports. Post-operative infections, treated with antibiotics, during hospital stay were scored until 30 days after surgery. Data were analysed with univariate and multivariate logistic regression analyses.

RESULTS

At least one post-operative glucose value was retrieved for 211/275 (77%) patients. The incidence of post-operative infections was 84/275 (31%). When corrected for factors associated with insulin resistance and surgical stress, post-operative glucose levels were found to be an independent risk factor for post-operative infections (odds ratio top quartile versus lowest quartile: 5.1; 95% confidence interval: 1.6-17.1; P=0.007).

CONCLUSION

Post-operative glucose levels appear to be an independent risk factor for infections after infrainguinal vascular surgery. This finding requires confirmation in a prospective study.

Management of Complex Groin Wounds: Preferred Use of the Rectus Femoris Muscle Flap

This study reviews our experience with the rectus femoris muscle flap for complex groin wound reconstruction. Over the past 5 years, the rectus femoris has become our routine method of groin wound reconstruction. The rectus femoris is harvested through a midanterior incision extending over the distal two-thirds of the thigh. The muscle is elevated on its pedicle and transposed into the groin wound defect either directly or through an intervening skin bridge. Hospital and outpatient records were reviewed for all patients undergoing groin wound reconstruction with this technique from 1999 through 2003. Thirty-seven rectus femoris muscle flaps were performed in 33 patients. The mean patient age was 65.3 years (range, 25 to 88 years). Thirty groin wounds (81.1 percent) occurred after infrainguinal revascularization, 23 (76.7 percent) of which contained prosthetic material. Five (21.7 percent) of these wounds had their prosthetic material removed at the time of reconstruction. The remaining seven groin wounds (18.9 percent) occurred after femoral vessel cannulation for either cardiac or transplant surgery. There were no intraoperative mortalities and no anastomotic hemorrhages. There were no flap losses. Thirty-five of the 37 treated wounds healed (94.6 percent), 26 primarily (70.3 percent) and nine (24.3 percent) after delayed healing and contracture. Reoperation was performed in one patient for flap readvancement and in three patients for prosthetic graft removal after initial flap reconstruction. Two patients (6.1 percent) died during their hospitalization with persistent open groin wounds after flap reconstruction. All muscle flap donor incisions healed, with only two (5.4 percent) experiencing minimal delayed healing. There were no donor-site wound infections and no donor sites required reoperation. Thirty-three groin wounds (89.2 percent) demonstrated culture-positive microbial infection, 15 (45.5 percent) of which were polymicrobial. The 30-day mortality rate was 15.2 percent and the 6-month mortality rate increased to 27.2 percent, with multisystem organ failure as the most common cause. The rectus femoris muscle flap is an effective and reliable means of complex groin wound reconstruction. The muscle flap is dependable and the donor site is not problematic, even in the presence of peripheral vascular disease. On the basis of our clinical results, we believe that the rectus femoris muscle flap is the flap of choice for groin wound reconstruction.

Endovascular native vessel recanalization to maintain limb perfusion after infected prosthetic vascular graft excision

Prosthetic vascular graft infection is an uncommon yet serious condition. Traditional management has included debridement, excision of the infected graft, and revascularization as needed. We report on two cases in which limb viability was maintained by using endovascular native vessel recanalization after excision of infected prosthetic grafts. This approach was successful in maintaining adequate limb perfusion in both cases. Endovascular native vessel recanalization should be considered as an option to maintain limb viability after excision of infected prosthetic vascular grafts, especially when autogenous conduit is lacking or limitation of the extent of surgery is desirable.

Cryopreserved arterial allograft reconstruction for peripheral graft infection

OBJECTIVE

This prospective, observational study evaluated the safety and efficacy of cryopreserved arterial allograft reconstruction in the management of major peripheral arterial graft infections.

METHODS

From April 1996 to May 2003, data from patients with major peripheral arterial graft infection who underwent graft excision and cryopreserved arterial allograft reconstruction were prospectively collected. Arterial allografts were harvested from multiple organ donors and cryopreserved at -80 degrees C. The patients were observed for survival, limb salvage, persistence or recurrence of infection, and allograft patency. The results were calculated with the Kaplan-Meier method.

RESULTS

During the 7-year study period, 17 patients (14 men, 3 women; mean age, 68 years) with major peripheral graft infection underwent graft excision and cryopreserved arterial allograft reconstruction. Eight patients (47%) had systemic sepsis, 5 (29%) had acute ischemia at the time of the allograft reconstruction, and 9 (53%) had experienced anastomotic rupture. Allograft reconstruction was performed as an emergency procedure in 7 patients (41%). There were no perioperative deaths or early amputations. Two patients had allograft ruptures in the groin during the early postoperative period. The mean follow-up period was 34 months (range, 8 to 80 months). There was no persistent or recurrent infection, and none of the patients received long-term (>3 months) antibiotic therapy. Reoperation for allograft revision, excision, or replacement was performed in 2 patients. The 18-month primary and secondary allograft patency rates were 68% and 86%; the overall limb salvage rate was 82% at 2 years.

CONCLUSION

Our experience with cryopreserved arterial allograft in the management of major peripheral bypass graft infection suggests that this technique seems to be a useful option for treating one of the most dreaded vascular complications.

Local Infections After Above-Knee Prosthetic Femoropopliteal Bypass for Intermittent Claudication

BACKGROUND

The use of prosthetic grafts in the treatment of intermittent claudication is still a controversy. Prosthetic bypass for this usually benign condition may in some cases lead to a graft infection. This potentially disastrous complication is difficult to manage.

METHODS

One hundred forty-one consecutive operations done on 129 patients between January, 1990 and December, 2001 in a single university vascular unit have been studied. Lymphatic complications and local infections have been related to preoperative risk factors, complications, secondary procedures, and outcome.

RESULTS

During a mean follow-up period of 42 months, lymph complications occurred after 18 operations, surgical site infection after 11 procedures, and graft infection after 17 operations. Eleven infected grafts were treated successfully without graft excision. Six of these grafts healed with antibiotics only. The risk of developing a local infection was significantly correlated with postoperative lymph fistula. Reoperative surgery was associated with graft infection. Graft infection caused by Staphylococcus aureus always warranted surgery, either local revision or graft excision.

CONCLUSIONS

The present series had a high frequency of graft infections. Our data suggest that a selective approach should be taken towards excision of infected femoropopliteal prostheses. The need for and extent of surgery should be individualized according to the clinical presentation of the graft infection and the type of bacteria involved. We advocate a conservative attitude towards surgical treatment of intermittent claudication.

An In Vitro Model to Compare the Antimicrobial Activity of Silver-Coated Versus Rifampicin-Soaked Vascular Grafts

In situ replacement of infected vascular grafts is an accepted alternative to total graft excision and extraanatomic replacement. Its success relies upon the ability of the newly inserted graft to resist recurrent infection. This study compares the efficacy of two methods used to reduce the risk of graft reinfection: rifampicin soaking versus silver bonding of grafts. The grafts' resistance to infection was tested in vitro in two protocols, each using a panel of seven common bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). The length of time the grafts remained free of organisms was compared between the groups. Both the silver graft and the rifampicin-soaked graft were significantly better than control graft at preventing bacterial growth on the graft surface. The rifampicin inhibited the growth of the gram-positive organisms, including MRSA, significantly better than the silver graft on days 2 and 3 (p < 0.001). Conversely, the silver graft was significantly more effective against the gram-negative organisms until day 4 (p < 0.0001). Both types of graft inhibit the in vitro growth of bacteria more effectively than controls, with rifampicin being most effective against gram-positive organisms and silver being best against the gram-negative organisms.

Does fibrin glue reduce complications after femoral artery surgery? A randomised trial

OBJECTIVES

to determine whether application of fibrin glue before closure of inguinal wounds reduces the incidence of lymphatic complications.

DESIGN

we a prospective randomised trial.

MATERIALS AND METHODS

224 consecutive patients were enrolled. The wounds were randomly assigned to standard closure (group A, n = 134) or closure with application of fibrin glue (group B, n = 132). The incidence of local lymphatic and non-lymphatic complications, the amount of lymphatic fluid collected, and the time to drain removal were compared in the groups.

RESULTS

the incidence of lymphatic complications was 19% in group A and 10% in group B (p = 0.027). The average drain output and the time to drain removal did not differ in the two groups. The total incidence of non-lymphatic local complications was 10% and did not differ in the two groups.

CONCLUSIONS

fibrin glue application is associated with a significant reduction in lymphatic complications.

Experimental treatment of vascular graft infection due to Staphylococcus epidermidis by in situ replacement with a rifampin-bonded polyester graft

In situ prosthetic graft replacement (ISPGR) of an infected prosthesis raises the risk of recurrent infection in the new graft, especially in cases involving drug-resistant microorganisms. The purpose of this animal study was to evaluate in situ replacement of a vascular graft infected by a highly rifampin-resistant strain of Staphylococcus epidermidis with the use of a rifampin-bonded polyester graft. Antibiotic bonding was obtained by soaking grafts in a high dose of rifampin solution (60 mg/mL). The infrarenal abdominal aorta of 20 dogs was replaced using a polyester prosthesis infected with a highly rifampin-resistant strain of Staphylococcus epidermidis. One week later, the 18 surviving animals were randomized into three groups. Group I (n = 6) did not undergo reoperation. Group II (n = 6) underwent ISPGR using a rifampin-bonded prosthesis. Group III (n = 6) underwent ISPGR using an untreated prosthesis. All surviving animals were killed 28 days after the first procedure. Infectious signs were noted and bacteriological study was carried out on explanted prostheses and various tissue samples. The findings of this experimental study show that soaking a polyester prosthesis in a high-dose rifampin solution can prevent reinfection after in situ replacement of a prosthesis infected by a highly rifampin-resistant Staphylococcus epidermidis.

Wound infections involving infrainguinal autogenous vein grafts: a current evaluation of factors determining successful graft preservation

PURPOSE

The purpose of this study was to review the natural history and clinical outcome of patients with infrainguinal autogenous graft infection (IAGI), to evaluate the effectiveness of attempted graft preservation, to determine those variables associated with graft salvage, and to better determine optimal treatment.

STUDY DESIGN

We retrospectively reviewed the records of patients undergoing infrageniculate vein grafts at three hospitals between 1994 and 2000 who had a wound infection involving the graft. Clinical and bacteriologic variables were analyzed and correlated with graft salvage, limb salvage, and clinical outcome.

RESULTS

During this 7-year period, 487 patients underwent an infrageniculate vein graft, and 68 (13%) had clinical evidence of IAGI. Twenty-seven patients presented with drainage from the wound, 15 with wound separation and cellulitis, 18 with soft tissue infection extending to the graft, 4 with an abscess and cellulitis, and 4 with bleeding. Ten patients (15%) had systemic symptoms (defined as a white blood cell count > 15,000 and temperature > 38.5 degrees C). Forty infections developed in the thigh, 17 in the groin, and 11 in the lower leg. An anastomosis was exposed in 15 patients. Wound cultures were positive for bacteria in 52 patients, and most infections were due to Staphylococcus aureus (18 patients) and S epidermidis (12 patients). Pseudomonas was cultured from seven infections. Twelve patients had polymicrobial infections. The interval from operation to infection ranged from 7 to 180 days. All patients were treated with oral antibiotics, 48 after intravenous antibiotics. Forty-five patients had operative debridement, including 18 who had muscle flap coverage. Four patients presented with hemorrhage, and three had immediate graft ligation and one graft excision. Follow-up ranged from 5 to 68 months (mean, 24.3 months), with 61 patients currently alive. Two patients died as a result of the IAGI (mortality rate, 2.9%). One had undergone a below-knee amputation, and one had a nonhealed wound but intact limb. Overall, 61 wounds (91%) healed, 4 patients required below-knee amputations, and 3 wounds did not heal. Fifty-eight grafts remained patent, 6 thrombosed, and 4 were ligated to control hemorrhage. Of the 61 wounds that healed, the time required for healing ranged from 7 to 63 days. No patient with bleeding died because of the acute episode. No patient had delayed hemorrhage. All 18 patients treated with a muscle flap healed. Bleeding (P <.001), elevated white blood cell count (P <.029), fever (P <.001), and renal insufficiency (creatinine level > 1.5; P <.056) were the only variables statistically significant in predicting graft failure or limb loss. With the use of life-table analysis, graft patency was 94%, 72%, and 72% at 1, 3, and 5 years, and limb salvage was 97%, 92%, and 92% at the same intervals, respectively.

CONCLUSIONS

Most patients with an IAGI can be successfully treated with graft and limb preservation. In contrast to earlier studies, an exposed anastomosis, interval to infection, or Pseudomonas infection is not associated with graft failure. Graft salvage is less likely in patinets with fever, leukocytosis, and renal insufficency, but because most grafts remained patent, graft preservation is recommended for these patients. Graft ligation or excision should be reserved for patients presenting with bleeding or sepsis.

Reduction of groin lymphatic complications by application of fibrin glue: preliminary results of a randomized study

Lymphoceles and lymph fistulas are common complications after exposure of the common femoral artery in the Scarpa triangle because of operative transsection of overlying lymphatics. The purpose of this prospective randomized study was to determine the incidence of groin lymphatic complications and to assess the impact of routine application of fibrin glue on lymphatic structures and subcutaneous tissue prior to closure. All patients undergoing exposure of the common femoral artery in the Scarpa triangle were included in this study. They were divided into two groups according to closure technique. In group A, closure was performed without fibrin glue. In Group B, fibrin glue was applied to lymphatic structures prior to closure. The efficacy of fibrin glue application was estimated on the basis of two criteria: incidence of local complications and amount of lymphatic fluid in the Redon drain. The preliminary findings suggest that application of fibrin glue leads to a significant reduction in the incidence of lymphatic complications after femoral artery exposure in the Scarpa triangle.

Infection-related exposure of the lower anastomosis of femorodistal bypass: salvage through use of pedicle muscle flaps

Wound dehiscence with exposure of the lower anastomosis is a limb- and life-threatening complication of femorodistal bypass. Plastic surgeons consider pedicle flaps to be unreliable in patients with arterial disease. Despite this opinion, we attempted to treat exposure complications using pedicle muscle flaps after careful study of vascularization on control angiography. The purpose of this report is to describe our results. From 1994 to 1997, infection-related exposure of the distal anastomosis was observed in three men and two women with a mean age of 76 years (range, 66 to 89 years). The exposed anastomosis was located on the dorsalis pedis artery in three cases, the anterior tibial artery in the upper third of the leg in one, and the anterior tibial artery in the lower third of the leg in one. The bypass material was a vein graft in three cases and a cuffed PTFE prosthesis in two cases. Bacteriological examination identified Staphylococcus aureus in three cases, Pseudomonas aeruginosa in one case, and both in one case. Two patients were diabetics and one was undergoing corticosteroid treatment. The anastomosis was covered with a pedicle muscle flap fashioned from the extensor digitorum in four cases and the lateral head of the gastrocnemius in one case. Our results showed that anastomoses on the anterior tibial artery and dorsalis pedis artery are at higher risk for infection-related exposure but this complication can be treated using pedicle muscle flaps. This alternative should be considered before bypass removal or amputation.

Intraoperative contamination of synthetic vascular grafts. Effect of glove change before graft implantation. A prospective randomised study

OBJECTIVES

to investigate the incidence of intraoperative graft contamination, bacterial species and the influence of change of surgeon's gloves on contamination.

DESIGN

a prospective randomised study.

MATERIALS AND METHODS

forty patients had implantation of synthetic vascular grafts. All patients received intraoperative cloxacillin (2.0 g) or clindamycin (0.6 g) intravenously. The procedures were randomised to two groups: Group 1 - surgeons changed the gloves before the first contact with the vascular prosthesis and Group 2 - operation without glove change. The growth of all bacterial species from graft segments and from the gloves was recorded. The susceptibility to antibiotics was tested.

RESULTS

the number of contaminated grafts was similar in the two groups. Growth of bacteria was recorded from 92.5% (37/40) of the graft segments and 33% (51/156) of glove imprints. Of the cultured species, 75% and 47%, respectively, were identified as coagulase-negative staphylococci (CNS). Twenty-eight per cent of CNS were resistant to cloxacillin, 15% to clindamycin, and 10% to cloxacillin and clindamycin. In all, 25% of the CNS strains were resistant to the prophylactic antibiotic used. In 50% of cases, the antibiogram of the CNS strain recovered from gloves agreed with that of the strain harvested from the graft.

CONCLUSIONS

a high incidence of graft contamination was found which was not reduced by changing gloves. However, changing gloves did seem to reduce the number of bacterial species.

Bacterial components inhibit fibroblast proliferation in vitro

Perigraft fluid from Staphylococcus epidermidis infected grafts in a mouse model significantly inhibits fibroblast proliferation (60-98% at 7 and 28 days), compared with perigraft fluid from sterile grafts. The fibroblast inhibitor was trypsin-heat resistant and dependent primarily upon the bacteria, not the host proinflammatory mediators or the vascular graft biomaterial. We tested the inhibitory properties of S. epidermidis strains RP62A (slime producer) and RP62NA (nonslime producer) and Staphylococcus aureus strain 502a, using an in vitro tritiated thymidine murine fibroblast (ATCC CCL-12) proliferation assay. Whole killed bacteria, disrupted bacteria (live and killed), bacterial supernatants, and purified cell wall products (peptidoglycan, teichoic acid, and lipoteichoic acid from disrupted bacteria) were studied. Significant fibroblast inhibition occurred for all three bacterial strains with disrupted bacteria (live or killed) and cell free bacteria derived supernatants. The fibroblast inhibitor from disrupted slime producing S. epidermidis was trypsin-heat resistant. The fibroblast inhibitor from disrupted S. aureus and supernatants for all three bacterial strains at 1 x 10(7) were trypsin-heat sensitive. Fibroblast inhibition was not dependent upon bacterial viability and not mediated by bacterial cell wall products. In conclusion, components of slime and nonslime producing S. epidermidis and S. aureus inhibit fibroblast proliferation.

Improved management of infrainguinal bypass graft infection with methicillin-resistant Staphylococcus aureus

BACKGROUND

There is considerable debate over the management of infected infrainguinal grafts. This report describes recent experience in this field and documents the change in clinical practice needed to deal with methicillin-resistant Staphylococcus aureus (MRSA).

METHODS

All infected infrainguinal grafts between January 1991 and July 1997 were reviewed. In the light of the findings, clinical practice was modified considerably. A further 1 year was audited prospectively up to August 1998.

RESULTS

Twenty-six patients were treated for 27 infrainguinal graft infections (25 prosthetic, two vein). Twenty were treated by complete graft excision as the initial therapy; graft preservation was attempted in six patients. Before 1995, the infecting organisms were predominantly Pseudomonas aeruginosa or methicillin-sensitive staphylococci. Subsequently all 14 patients treated up to 1997 had infection with MRSA. The overall amputation rate was 17 of 26; ten amputations were in patients with MRSA. Four patients died, all with MRSA sepsis. As a result of this experience a policy of complete isolation was adopted for all patients infected with MRSA. In the 12 months since this policy was introduced, 77 infrainguinal grafts (61 vein, 16 prosthetic) have been inserted. Two grafts (3 per cent) have become infected, necessitating graft excision and amputation.

CONCLUSION

MRSA infection of an infrainguinal graft is a serious complication with high associated amputation and mortality rates. Isolation and barrier nursing appeared to contain the problem.

Microbial biofilms: their development and significance for medical device-related infections

Microbial adhesion and biofilm formation on medical devices represent a common occurrence that can lead to serious illness and death. The process by which bacteria and yeast colonize open and closed implants is fairly complicated and involves a series of steps commencing with deposition of host substances onto the material. Prevention and treatment of established biofilms with antimicrobial agents are difficult because the organisms are encased within a protected microenvironment. Efforts to reduce adhesion using specially developed materials, such as hydrophilic or heparin coated, have had modest success once applied to the patient. The reason, at least for the most part, is the diverse milieu into which devices are placed and the multitude of ways in which organisms can colonize surfaces. A better understanding of the process is required, and the knowledge gained must be used to devise new strategies as alternatives to the traditional employment of antibiotics. These new approaches may still use antibiotics but at different concentrations (low to prevent and high to treat infection) and in a different manner (perhaps spiked therapy in which there is a delay between doses to reduce the risk of drug resistance and impact on normal flora). The possibility of applying functional foods to patient management should also be pursued.

Bacterial resistance of refrigerated and cryopreserved aortic allografts in an experimental virulent infection model

PURPOSE

The bacterial resistance of refrigerated and cryopreserved aortic allografts in a highly virulent infection in a dog model was studied.

METHODS

The infrarenal aorta of 12 dogs was replaced with either a cryopreserved aortic allograft (group I, n = 6) or a refrigerated aortic allograft (group II, n = 6) in infected sites. Allografts were harvested from dogs and stored for 1 week, either by cryopreservation (-140 degrees C) or refrigerated method (4 degrees C), in a preservation medium. At the time of implantation, induction of infection was achieved with an infected piece of knitted Dacron placed just beneath the allograft. The Dacron was contaminated in vitro by soaking it in a solution with Staphylococcus aureus PR209. All 12 dogs received no adjunct antibiotic or antithrombotic therapy. Four weeks after implantation, the animals were killed to recover the grafts for bacteriological and histological analyses. Bacterial results were expressed as colony-forming units (CFU)/cm2 of graft material.

RESULTS

In group I, only one allograft grew bacteria at 2. 16 x 10(6 )CFU/cm2, with a blood culture positive for S aureus. In group II, one dog died at 3 weeks from a false septic aneurysm rupture, all the allografts were infected (P <.05) with a mean bacterial count of 9.41 +/- 6.8 x 10(4) CFU/cm2, and three blood cultures were positive for S aureus. The patency of the grafts was analyzed at the time of recovery. Three laminar thrombi without occlusion were present in group I; none were present in group II. A better preserved endothelium in group I was revealed by means of histologic analysis staining with factor VIII antibody before implantation. After 4 weeks of implantation in the infected site, infected allografts presented polynuclear infiltrates in the media with a high degree of inflammatory reaction, and endothelial recovery was more significant in group I, with numerous young plump cells.

CONCLUSION

This study demonstrates that cryopreserved allografts implanted in infected sites in a dog model can produce greater bacterial resistance.

Should vein be saved for future operations? A 15-year review of infrainguinal bypasses and the subsequent need for autogenous vein

The decision to use prosthetic or autogenous vein as the initial conduit for first-time vascular bypass of the lower extremity depends in part on the likelihood of subsequent need for autogenous conduit for another leg or heart bypass. The true frequency of these later events is not known. To answer this question, we analyzed a database of infrainguinal and coronary artery bypasses (CABG) performed at one institution between January 1980 and July 1995, to determine how many patients required subsequent infrainguinal bypass or CABG after their initial leg bypass. Five hundred and seventy-two infrainguinal bypasses were performed on 440 patients (mean age 63.9); average follow-up was 5.6 years. The clinical philosophy favored autogenous vein for first bypass, which was used in 84% of first operations performed during the study period while prosthetic material was used in 16%. For patients in which vein was used for the first operation, and who went on to have a second operation, the use of prosthetic conduit rose from 16% of operations to 27% (p < 0.05). The rate of subsequent CABG after leg bypass was very low, 2% at 5 years, 3% at 10 years. The cumulative probability of requiring a subsequent infrainguinal bypass was 27% at 5 years, 32% at 10 years. Of these, 46% were ipsilateral and 54% were contralateral. Considering only subsequent tibial bypasses (where vein might be considered obligatory), the cumulative 5-year rate of subsequent leg bypass was only 13%. Another bypass was most likely to occur within the first 3 years, rarely thereafter. In summary, after primary infrainguinal bypass, additional procedures using vein may arise in 1/4 to 1/3 of patients, mostly in the first 3 years. However, only 13% will definitely need vein for tibial bypass in 5 years, and subsequent CABG is uncommon.

Bacterial products primarily mediate fibroblast inhibition in biomaterial infection

PURPOSE

The stimulation of fibroblast growth is essential for the normal healing and tissue integration of biomaterials. The local elevation of proinflammatory mediators in infected perigraft fluid (PGF) may inhibit this growth. We sought to determine whether infected PGF inhibited fibroblast growth, and, if so, whether this was primarily dependent on the biomaterial, bacteria, or host.

METHODS

In vivo Dacron or expandable polytetra-fluoroethylene (ePTFE) grafts, sterile or colonized with slime-producing (RP-62A, viable or formalin-killed) or nonslime-producing (RP-62NA) Staphylococcus epidermidis (1 x 10(7) CFU/cm2), were implanted in Swiss Webster mice, and the PGF was harvested at 7 and 28 days. Antibodies to tumor necrosis factor alpha, interleukin 1 alpha, interferon gamma (7 micrograms/day), and indomethacin (50 micrograms/day) were administered by microinfusion pumps for 7 days and the PGF was harvested. Inhibition of the proinflammatory mediators was confirmed by enzyme-linked immunosorbant assay. The nontreated, heat-treated, or trypsin-digested in vivo PGF was incubated with an in vitro [3H]thymidine murine fibroblast (ATCC CCL-12) proliferation assay.

RESULTS

Fibroblast inhibition was significant at 7 and 28 days with infected PGF incubation compared with sterile and was not dependent on bacterial slime production or viability. Dacron sterile PGF did not significantly inhibit fibroblasts compared with control, whereas sterile ePTFE stimulated (P < 0.05) fibroblasts. Treatment of the PGF with proinflammatory cytokines, heat, and trypsin failed to reverse fibroblast inhibition in the infected state.

CONCLUSION

Biomaterial infection is associated with fibroblast inhibition that is dependent primarily on bacterial products and not the host or biomaterial. Conservative intervention strategies for graft infection need to address the problem of poor healing as well as bacterial clearance.

A completely biological tissue-engineered human blood vessel

Mechanically challenged tissue-engineered organs, such as blood vessels, traditionally relied on synthetic or modified biological materials for structural support. In this report, we present a novel approach to tissue-engineered blood vessel (TEBV) production that is based exclusively on the use of cultured human cells, i.e., without any synthetic or exogenous biomaterials. Human vascular smooth muscle cells (SMC) cultured with ascorbic acid produced a cohesive cellular sheet. This sheet was placed around a tubular support to produce the media of the vessel. A similar sheet of human fibroblasts was wrapped around the media to provide the adventitia. After maturation, the tubular support was removed and endothelial cells were seeded in the lumen. This TEBV featured a well-defined, three-layered organization and numerous extracellular matrix proteins, including elastin. In this environment, SMC reexpressed desmin, a differentiation marker known to be lost under standard culture conditions. The endothelium expressed von Willebrand factor, incorporated acetylated LDL, produced PGI2, and strongly inhibited platelet adhesion in vitro. The complete vessel had a burst strength over 2000 mmHg. This is the first completely biological TEBV to display a burst strength comparable to that of human vessels. Short-term grafting experiment in a canine model demonstrated good handling and suturability characteristics. Taken together, these results suggest that this novel technique can produce completely biological vessels fulfilling the fundamental requirements for grafting: high burst strength, positive surgical handling, and a functional endothelium.

Outcomes in the management of vascular prosthetic graft infections confined to the groin: a reappraisal

The management of vascular prosthetic graft infections confined to the groin continues to be controversial. To critically evaluate this problem, we reviewed the records of our vascular registry from December 1992 through February 1995 and found 17 incidences of groin sepsis involving a vascular prosthesis in 10 patients. These included a proximal prosthetic femoropopliteal bypass (n = 6), an aortobifemoral graft limb (n = 5), an ileofemoral bypass (n = 3), a prosthetic femoral patch (n = 2), and an aortofemoral/femorofemoral bypass (n = 1). The mean age of these patients was 65 years. Six patients were diabetic, four were on systemic steroids, and two were diabetic and on steroids. All infections were Szilagyi grade III including three in which the patients presented with local hemorrhage. Treatment consisted of irrigation, radical debridement with or without in situ graft replacement, and local rotational muscle flap coverage in nine cases, graft excision with extra-anatomic (obturator ileofemoral bypass) graft replacement in six cases, and excision alone in two cases. Of the 17 infections treated operatively and followed from 1 week to 18 months (median 5 months), eight (47%) showed no evidence of recurrence, six (35%) recurred, two (12%) caused early death, and one resulted in a thrombosed graft requiring extra-anatomic reconstruction. Of the nine infected grafted treated locally with muscle flaps, six showed recurrent infection from 3 weeks to 15 months and one thrombosed for a total local treatment failure rate of 78%. Only two grafts are free of infection at 4 and 5 months, respectively. Of the six incidences of infection treated with obturator bypass, four (66%) are free of infection and two resulted in patient death; both infections treated with excision alone were eradicated but resulted in a major lower extremity amputation. These data question the growing acceptance of debridement and local muscle flap coverage for the treatment of all prosthetic vascular graft infections confined to the groin, especially in patients who are diabetic or on systemic steroids.