Chapter 47 - Vascular graft infections Flashcards
Rate of graft infections in general
0.2-5%
Early infection rate < 30d
1-2%
Graft infections are more likely in:
1) emergency 2) femoral involvement 3) subcutaneous tunnel used
Rate of OAAA infection and EVAR infection
0.2% for both
Rate of bare metal stent infection
< 0.1%
Early vs late infection defined by
4 months
Szilagyi class
Post-op wound infection Grade 1: cellulitis with wound involvement Grade 2: subcutaneous tissue Grade 3: vascular prosthesis involvement
Bunt’s class
Extent of graft involved P0: cavitary graft P1: non-cavitary P2: extracavitary infection originating in cavity P3: patch infection GEE GEF Aortic stump sepsis
Early infection more likely with:
1) mostly Szilagyi class III 2) extracavitary 3) occurs after discharge 4) hospital-acquired virulence
Late infections more likely associated with:
1) low virulent organism (staph epi, candida sp) 2) low culture likelihood 3) cavitary can be real late 40 months
Elek + Conen 1957 discovered…
Discovered that single braided silk reduces inoculum required for inrection
Risk of infections factors:
1) high virulence 2) large inoculum 3) depressed immunity 4) remote site from host defence
Pathogenesis of graft infection
1) adhesion of bacteria to surface 2) Formation of microcolonies 3) Activation of host defenses 4) inflammatory response
Bacteria adhere to polyester compared to PTFE
polyester 10-100x more easily than PTFE
Gram + make this to increase adherence
extracellular glycocalyx (mucin)
Incorporation of graft impaired by:
1) seroma 2) hematoma 3) increase acidity due to excessive inflammation 4) local ischemia 5) matrix metalloproteinase made by TNF macrophages
Source of infection to graft:
1) preop contamination via wound 2) bacteremic seeding 3) mechanical erosion into bowel 4) genitourinary tract erosion 5) skin erosion 6) contiguous infectious process
Reoperation wound has bacteria culture positive in:
10-20%
Thrombosed graft has bacteria culture positive in
50-70%
Pseudoaneurysm at anastamotic sites has bacterial culture in
80%
Rate of GEE/GEF after aortic graft
0.4-2%
Things that impair host defense
1) malnutrition 2) malignancy 3) lymphoproliferative disorder 4) autoimmune disease 5) chronic kidney disease 6) liver disease 7) drugs 8) diabetes
Most prevalent pathogen in infected grafts
Staph aureus 25-50%
Growth negative cultures common with these organisms
1) Staph epi 2) candida 3) other coag neg bacteria
Gram negative bacteria characteristics
1) high virulence 2) endotoxin compromise structure (elastase, alkaline protease
Fungal and myobacterium characteristics
rare, only in immunocompromised or have ongoing infection elsewhere
MRSA rate in general population
2%
MRSA rate in LTC
23-49%
Prevention of graft infection
1) avoid pre-hospitalization 2) scrub patient 1-3 days pre-op with alcohol baed soap 3) control remote infection first 4) remove hair 5) protect graft from skin 6) avoid GI cocomitant procedures 7) antibiotics 30-60 min prior to skin incision 8) close dead space, close skin with minimal tension
Routine rifampin on infections
Early: 4.4% without, 2.7% with Late: 0.6% without, 0.3% with inconclusive
Prophylactic antibiotic choice
Ancef 2g q8h or Cefuroxime 1.5g q12h Vancomycin 1g q12 - for reoperations and MRSA Pen allergy: Daptomycin 4 mg/kg daily Levofloxacin 500 mg daily Clindamycin 900 mg q8h
Prophylactic antibiotics for dental, colonoscopy and cystoscopy
within 3 months of OR: Amoxicillin 2g 1 hr pre Clindamycin 600 mg 1 hr pre
Rate of positive blood culture in graft infection
< 5%
Diagnostic criteria for CT for infection
1) Loss of normal tissue plane (fat density) in perigraft 2) fluid and gas around graft structures 3) pseudoaneurysm 4) hydronephrosis 5) adjacent vertebral/bony osteomyelitis
When is gas around graft abnormal
After 2-3 months post-op
Best use for ultrasound in ruling out infection
1) P1, P2, P3 extracavitary 2) color duplex to identify pseudoaneurys 3) Access graft patency
MRI better than CT in infection for:
distinguish perigraft fluid vs fibrosis
WBC scan radionuclide types
1) Gallium 67 citrate 2) Indium 111-labelled leukocytes 3) Technetium Tc99m hexametazime labelled-leukocytes (80-90% PPV) 4) IgG scans
When is WBC scan not useful
within 3-6 months post-op
Ways to identify infection
1) CT 2) US 3) MRI 4) WBC scan 5) endoscopy 6) CT guided aspiration 7) exploratory surgery
Culture techniques
1) Mechanical tissue grinding 2) broth incubation trypticase soy broth 3) grow 5-7 days
When is it ok to preserve graft in infections
1) short length infection 2) anastomosis sparing 3) early < 4 months 4) Single gram + 5) Extracavitary 6) Low virulence 7) no systemic sepsis 8) PTFE > dacron
Organisms that cannot have graft preservation if concurrent sepsis
1) Pseudomonas 2) Klebsiella 3) Serratia 4) Proteus 5) E coli
Technique for graft preservation
1) serial I+D with cytotoxic solution 2) antibiotic bead (polymethyl methacrylate) 3) negative pressure wound therapy 4) myoplasty
Deciding whether to do concurrent reconstruction
1) intraop occlusion with tournequet and doppler 2) look for pulsatile waveform and pressure > 40 mm Hg
Graft excision from aorta - principle
1) needed in GEE/GEF, invasive infection, sepsis, abscess 2) Fgarty occlusion 3) Ureteric stents 4) double layer interrupted monofilaments 5) I+D tunnel 6) omental coverage of stump 7) drains +/- betadine irrigation 8) repeat CT 7-10 days 9) preserve 1 internal iliac
Improvements in recent decades
1) decrease early limb loss 2) decrease residual aortic infection 3) decrease stump blowout 4) decrease recurrent ex situ infection 5) decrease midterm mortality
Patency of Ax-unifem at 6 months
94%
Patency of Ax-unipop at 6 months
42%
Who developed NAIS
Clagett 1993 Nevelsteen 1995
Risk of calf compartment in SFV harvest after previous GSV harvest
12%
Risk of venous insufficiency after SFV harvest
15%
Pantaloon technique for aortic sizes:
18-26 mm
Aortic sizes > this will need ex situ reconstruction
28 mm
Benefit of NAIS over ex situ
1) decrease mortality 2) decrease amputation 3) improve patency 4) decrease recurrent infection
NAIS primary, secondary patency at 6 years and amputation free-survival
primary 81% secondary 91% amputation free 89%
NAIS mortality
10%
NAIS 5 year survival
52%
Contraindication to NAIS
1) GEE/GEF 2) virulent Gram -
Risk factors for stenosis after NAIS:
1) CAD 2) smoker 3) SFV < 7 mm
Recurrent infection in Abx-soaked graft
10-20% (higher in Gram - or MRSA)
When to use abx-soaked graft
1) localized/segmental 2) low grade biofilm infection 3) Coagulase-negative staph epi 4) extracavitary
Principles of operating on graft infection
1) pre-op daptomycin or vancomycin 3 d prior 2) wide I+D 3) excise anastomosis 4) rifampin soak 60 mg/ml 5) Myoplasty or omental pedicle 6) antibiotics x 6 weeks
Who first used cryografts
Kieffer 1993
1st gen Allograft 3 year rate of aneurysm/dilation
17%
1st gen Allograft 3 year rate of stenosis/occlusion
20%
Principle of using allograft
1) thaw before use 2) end-to-end anastomosis 3) avoid allograft to allograft 4) ligate branches not just clip 5) pledget with allograft pieces 6) Gentamycin fibrin glue at anastomosis 7) muscle and omentum for coverage 8) antibiotics for 6 weeks
Principles of antibiotics therapy
Vancomycin + one of: 1) Piptazo 3.375 q6h 2) Cefapime 2g q8-12h 3) Levofloxacin 500 mg daily
Antibiotics in treating MRSA
Daptomycin 6 mg/kg daily
Pseudomonas antibiotics coverage
Double cover with 1) 3rd or 4th gen cephalosporin 2) piptazo 3) aminoglycoside 4) fluoroquinolones 5) carbapenem/monobactam
Oral antibiotiocs for discharge home after non-MRSA infections of graft
1) amox clav 2) fluoroquinolone
Antibiotic bead ingredient
1) PMMA powder 2) liquid catalyst 3) antibiotics: Vanco 1g Dapto 1-1.5 Tobra 1.2 Gentamycin 1g
Muscle flaps possible
1) Sartorius 2) rectus abdominus 3) rectus femoris 4) gracilis
Surgical mortality in EVAR infected explant
10-30%
Reinfection in EVAR infected explant
5-10%
Selection criteria for open surgical technique
