Overview
Definition:
Bypass graft infection refers to a serious complication involving microbial colonization and subsequent inflammation of a prosthetic vascular graft used to bypass occluded or diseased native arteries
it can range from superficial wound dehiscence to deep graft abscess and systemic sepsis
Excision of the infected graft is often necessary, frequently followed by reconstruction using extra-anatomic bypasses to restore perfusion to the limb or organ while eradicating the source of infection.
Epidemiology:
Infection rates vary based on graft material, location, and patient comorbidities, typically ranging from 1-5% for infrainguinal bypasses and potentially higher for aortic or prosthetic infections
Risk factors include diabetes mellitus, obesity, malnutrition, immunosuppression, prolonged operative time, and intraoperative contamination.
Clinical Significance:
Bypass graft infection is a limb- or life-threatening complication
Early diagnosis and appropriate management, including complete graft excision and revascularization, are crucial to prevent graft failure, limb loss, hemorrhage, and systemic sepsis
Understanding the principles of management is vital for surgical residents preparing for DNB and NEET SS examinations.
Clinical Presentation
Symptoms:
Fever and chills
Localized wound erythema, induration, and tenderness
Increasing incisional pain
Purulent drainage from the wound or suture line
Claudication or worsening ischemic symptoms if the graft is compromised
Palpable pulsatile mass or a lack of pulsations in the graft or distal vessels
Bruit over the graft site.
Signs:
Wound dehiscence with purulent discharge
Localized warmth and erythema
Palpable tenderness over the graft
Pulsatile mass suggestive of pseudoaneurysm
Absent distal pulses or new onset of absent pulses
Systemic signs of infection: tachycardia, hypotension, leukocytosis.
Diagnostic Criteria:
Diagnosis is typically based on a combination of clinical suspicion, laboratory findings (elevated CRP, leukocytosis), and microbiological evidence (positive cultures from wound drainage or during surgery)
Imaging studies are crucial for defining the extent of infection and planning management.
Diagnostic Approach
History Taking:
Detailed history of the index surgery, including graft material, operative duration, and any intraoperative complications
Onset and progression of symptoms
Presence of fever, chills, or wound drainage
Assessment of limb ischemia symptoms
Review of comorbidities like diabetes, renal insufficiency, and immunosuppression.
Physical Examination:
Thorough examination of the surgical wound for signs of infection (erythema, induration, discharge)
Palpation for tenderness, warmth, and pulsatility over the graft
Auscultation for new or altered bruits
Assessment of distal pulses and perfusion of the affected limb
Examination for signs of systemic sepsis.
Investigations:
Laboratory: Complete Blood Count (CBC) with differential, C-reactive protein (CRP), Erythrocyte Sedimentation Rate (ESR)
Microbiology: Wound cultures and Gram stain if drainage present
Imaging: Ultrasound with Doppler to assess graft patency and identify peri-graft fluid collections
CT angiography (CTA) or MR angiography (MRA) to delineate the extent of graft infection, identify abscesses, pseudoaneurysms, and involvement of adjacent structures
it is crucial for planning extra-anatomic bypass
Plain radiography to rule out gas in the graft or adjacent tissues.
Differential Diagnosis:
Seroma
Hematoma
Wound dehiscence without infection
Superficial wound infection
Graft thrombosis
Adjacent soft tissue infection
Pseudoaneurysm without infection.
Management
Initial Management:
Broad-spectrum intravenous antibiotics covering gram-positive and gram-negative organisms, including anaerobes
Wound exploration and drainage if significant abscess is present
Hemodynamic stabilization if septic shock is suspected
Consultation with vascular surgery and infectious disease specialists.
Medical Management:
Empirical antibiotic therapy should be guided by local resistance patterns and initiated promptly
Once cultures are available, antibiotic therapy should be tailored to the identified pathogen and its sensitivities
Duration of antibiotic therapy is typically prolonged, often 4-6 weeks or longer, depending on the extent of infection and graft material
Oral suppressive therapy may be considered after initial IV treatment.
Surgical Management:
The cornerstone of management is complete excision of the infected prosthetic graft
This is typically followed by debridement of all infected tissue
Reconstruction is then performed, most commonly with extra-anatomic bypasses (e.g., axillofemoral, femoro-femoral) using prosthetic or autologous materials (e.g., cryopreserved allograft, vein)
In situ reconstruction is generally avoided in the presence of gross infection
For infrainguinal bypasses, limb salvage is paramount
In certain select cases with contained, early infection and no abscess, in situ treatment with aggressive debridement and prolonged antibiotics may be considered, but this is controversial
Definitive treatment for aortic graft infection often involves removal and extra-anatomic bypass, or sometimes in situ repair with rifampicin-soaked grafts in highly selected patients.
Supportive Care:
Aggressive wound care and dressing changes
Nutritional support to aid healing
Management of comorbidities
Close monitoring for signs of recurrent infection or graft complications
Physical therapy for rehabilitation
Pain management.
Complications
Early Complications:
Hemorrhage from the explanted graft bed
Graft thrombosis of the extra-anatomic bypass
Wound dehiscence
Graft infection in the extra-anatomic bypass
Systemic sepsis
Anastomotic leak.
Late Complications:
Chronic wound problems
Recurrent graft infection
Stenosis or occlusion of the extra-anatomic bypass
Limb ischemia
Amputation
Fistula formation (e.g., aortoenteric fistula).
Prevention Strategies:
Strict aseptic techniques during surgery
Preoperative antibiotics
Use of antibiotic-soaked grafts (controversial)
Careful handling of prosthetic material
Minimizing operative time
Meticulous hemostasis
Appropriate wound closure
Early recognition and prompt management of any wound issues postoperatively.
Prognosis
Factors Affecting Prognosis:
Extent and location of infection (e.g., aortic vs
infrainguinal)
Virulence of the pathogen
Patient's overall health status and comorbidities
Timeliness and adequacy of surgical intervention
Successful revascularization with extra-anatomic bypass
Response to antibiotic therapy.
Outcomes:
Limb salvage rates can be high (up to 80-90%) for infected infrainguinal bypasses managed with excision and extra-anatomic bypass, but are lower for extensive aortic graft infections
Mortality rates are significant, particularly with untreated or inadequately treated aortic graft infections
Graft patency for extra-anatomic bypasses is generally lower than for in situ bypasses, especially in the long term.
Follow Up:
Long-term follow-up is essential, including regular clinical assessments and duplex ultrasound examinations to monitor for patency of the extra-anatomic bypass and any signs of recurrent infection
Patients require lifelong monitoring due to the risk of late complications
Patients should be educated on symptoms of infection and limb ischemia.
Key Points
Exam Focus:
Complete excision of infected prosthetic graft is the gold standard
Extra-anatomic bypass (e.g., axillofemoral) is the preferred method for revascularization after prosthetic graft removal
Differentiate between contained infection and frank graft abscess
Understand indications for in situ repair vs
excision
Recognize risk factors for graft infection.
Clinical Pearls:
High index of suspicion for graft infection in any patient with a history of prosthetic vascular surgery presenting with fever, wound issues, or ischemic symptoms
CT angiography is crucial for delineating the extent of infection and planning reconstruction
Consider fungal or atypical bacterial infections in immunocompromised hosts
Prolonged course of antibiotics is usually required.
Common Mistakes:
Attempting to salvage an infected graft in situ without complete excision
Inadequate debridement of infected tissue
Premature cessation of antibiotic therapy
Underestimating the severity of aortic graft infection
Failure to perform adequate imaging preoperatively
Not considering distal embolization from an infected graft.