Chapter 47 - Vascular graft infections

Question 1

Rate of graft infections in general

Answer 1

0.2-5%

Question 2

Early infection rate < 30d

Answer 2

1-2%

Question 3

Graft infections are more likely in:

Answer 3

1) emergency 2) femoral involvement 3) subcutaneous tunnel used

Question 4

Rate of OAAA infection and EVAR infection

Answer 4

0.2% for both

Question 5

Rate of bare metal stent infection

Answer 5

< 0.1%

Question 6

Early vs late infection defined by

Answer 6

4 months

Question 7

Szilagyi class

Answer 7

Post-op wound infection Grade 1: cellulitis with wound involvement Grade 2: subcutaneous tissue Grade 3: vascular prosthesis involvement

Question 8

Bunt’s class

Answer 8

Extent of graft involved P0: cavitary graft P1: non-cavitary P2: extracavitary infection originating in cavity P3: patch infection GEE GEF Aortic stump sepsis

Question 9

Early infection more likely with:

Answer 9

1) mostly Szilagyi class III 2) extracavitary 3) occurs after discharge 4) hospital-acquired virulence

Question 10

Late infections more likely associated with:

Answer 10

1) low virulent organism (staph epi, candida sp) 2) low culture likelihood 3) cavitary can be real late 40 months

Question 11

Elek + Conen 1957 discovered…

Answer 11

Discovered that single braided silk reduces inoculum required for inrection

Question 12

Risk of infections factors:

Answer 12

1) high virulence 2) large inoculum 3) depressed immunity 4) remote site from host defence

Question 13

Pathogenesis of graft infection

Answer 13

1) adhesion of bacteria to surface 2) Formation of microcolonies 3) Activation of host defenses 4) inflammatory response

Question 14

Bacteria adhere to polyester compared to PTFE

Answer 14

polyester 10-100x more easily than PTFE

Question 15

Gram + make this to increase adherence

Answer 15

extracellular glycocalyx (mucin)

Question 16

Incorporation of graft impaired by:

Answer 16

1) seroma 2) hematoma 3) increase acidity due to excessive inflammation 4) local ischemia 5) matrix metalloproteinase made by TNF macrophages

Question 17

Source of infection to graft:

Answer 17

1) preop contamination via wound 2) bacteremic seeding 3) mechanical erosion into bowel 4) genitourinary tract erosion 5) skin erosion 6) contiguous infectious process

Question 18

Reoperation wound has bacteria culture positive in:

Answer 18

10-20%

Question 19

Thrombosed graft has bacteria culture positive in

Answer 19

50-70%

Question 20

Pseudoaneurysm at anastamotic sites has bacterial culture in

Answer 20

80%

Question 21

Rate of GEE/GEF after aortic graft

Answer 21

0.4-2%

Question 22

Things that impair host defense

Answer 22

1) malnutrition 2) malignancy 3) lymphoproliferative disorder 4) autoimmune disease 5) chronic kidney disease 6) liver disease 7) drugs 8) diabetes

Question 23

Most prevalent pathogen in infected grafts

Answer 23

Staph aureus 25-50%

Question 24

Growth negative cultures common with these organisms

Answer 24

1) Staph epi 2) candida 3) other coag neg bacteria

Question 25

Gram negative bacteria characteristics

Answer 25

1) high virulence 2) endotoxin compromise structure (elastase, alkaline protease

Question 26

Fungal and myobacterium characteristics

Answer 26

rare, only in immunocompromised or have ongoing infection elsewhere

Question 27

MRSA rate in general population

Answer 27

2%

Question 28

MRSA rate in LTC

Answer 28

23-49%

Question 29

Prevention of graft infection

Answer 29

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

Question 30

Routine rifampin on infections

Answer 30

Early: 4.4% without, 2.7% with Late: 0.6% without, 0.3% with inconclusive

Question 31

Prophylactic antibiotic choice

Answer 31

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

Question 32

Prophylactic antibiotics for dental, colonoscopy and cystoscopy

Answer 32

within 3 months of OR: Amoxicillin 2g 1 hr pre Clindamycin 600 mg 1 hr pre

Question 33

Rate of positive blood culture in graft infection

Answer 33

< 5%

Question 34

Diagnostic criteria for CT for infection

Answer 34

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

Question 35

When is gas around graft abnormal

Answer 35

After 2-3 months post-op

Question 36

Best use for ultrasound in ruling out infection

Answer 36

1) P1, P2, P3 extracavitary 2) color duplex to identify pseudoaneurys 3) Access graft patency

Question 37

MRI better than CT in infection for:

Answer 37

distinguish perigraft fluid vs fibrosis

Question 38

WBC scan radionuclide types

Answer 38

1) Gallium 67 citrate 2) Indium 111-labelled leukocytes 3) Technetium Tc99m hexametazime labelled-leukocytes (80-90% PPV) 4) IgG scans

Question 39

When is WBC scan not useful

Answer 39

within 3-6 months post-op

Question 40

Ways to identify infection

Answer 40

1) CT 2) US 3) MRI 4) WBC scan 5) endoscopy 6) CT guided aspiration 7) exploratory surgery

Question 41

Culture techniques

Answer 41

1) Mechanical tissue grinding 2) broth incubation trypticase soy broth 3) grow 5-7 days

Question 42

When is it ok to preserve graft in infections

Answer 42

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

Question 43

Organisms that cannot have graft preservation if concurrent sepsis

Answer 43

1) Pseudomonas 2) Klebsiella 3) Serratia 4) Proteus 5) E coli

Question 44

Technique for graft preservation

Answer 44

1) serial I+D with cytotoxic solution 2) antibiotic bead (polymethyl methacrylate) 3) negative pressure wound therapy 4) myoplasty

Question 45

Deciding whether to do concurrent reconstruction

Answer 45

1) intraop occlusion with tournequet and doppler 2) look for pulsatile waveform and pressure > 40 mm Hg

Question 46

Graft excision from aorta - principle

Answer 46

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

Question 47

Improvements in recent decades

Answer 47

1) decrease early limb loss 2) decrease residual aortic infection 3) decrease stump blowout 4) decrease recurrent ex situ infection 5) decrease midterm mortality

Question 48

Patency of Ax-unifem at 6 months

Answer 48

94%

Question 49

Patency of Ax-unipop at 6 months

Answer 49

42%

Question 50

Who developed NAIS

Answer 50

Clagett 1993 Nevelsteen 1995

Question 51

Risk of calf compartment in SFV harvest after previous GSV harvest

Answer 51

12%

Question 52

Risk of venous insufficiency after SFV harvest

Answer 52

15%

Question 53

Pantaloon technique for aortic sizes:

Answer 53

18-26 mm

Question 54

Aortic sizes > this will need ex situ reconstruction

Answer 54

28 mm

Question 55

Benefit of NAIS over ex situ

Answer 55

1) decrease mortality 2) decrease amputation 3) improve patency 4) decrease recurrent infection

Question 56

NAIS primary, secondary patency at 6 years and amputation free-survival

Answer 56

primary 81% secondary 91% amputation free 89%

Question 57

NAIS mortality

Answer 57

10%

Question 58

NAIS 5 year survival

Answer 58

52%

Question 59

Contraindication to NAIS

Answer 59

1) GEE/GEF 2) virulent Gram -

Question 60

Risk factors for stenosis after NAIS:

Answer 60

1) CAD 2) smoker 3) SFV < 7 mm

Question 61

Recurrent infection in Abx-soaked graft

Answer 61

10-20% (higher in Gram - or MRSA)

Question 62

When to use abx-soaked graft

Answer 62

1) localized/segmental 2) low grade biofilm infection 3) Coagulase-negative staph epi 4) extracavitary

Question 63

Principles of operating on graft infection

Answer 63

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

Question 64

Who first used cryografts

Answer 64

Kieffer 1993

Question 65

1st gen Allograft 3 year rate of aneurysm/dilation

Answer 65

17%

Question 66

1st gen Allograft 3 year rate of stenosis/occlusion

Answer 66

20%

Question 67

Principle of using allograft

Answer 67

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

Question 68

Principles of antibiotics therapy

Answer 68

Vancomycin + one of: 1) Piptazo 3.375 q6h 2) Cefapime 2g q8-12h 3) Levofloxacin 500 mg daily

Question 69

Antibiotics in treating MRSA

Answer 69

Daptomycin 6 mg/kg daily

Question 70

Pseudomonas antibiotics coverage

Answer 70

Double cover with 1) 3rd or 4th gen cephalosporin 2) piptazo 3) aminoglycoside 4) fluoroquinolones 5) carbapenem/monobactam

Question 71

Oral antibiotiocs for discharge home after non-MRSA infections of graft

Answer 71

1) amox clav 2) fluoroquinolone

Question 72

Antibiotic bead ingredient

Answer 72

1) PMMA powder 2) liquid catalyst 3) antibiotics: Vanco 1g Dapto 1-1.5 Tobra 1.2 Gentamycin 1g

Question 73

Muscle flaps possible

Answer 73

1) Sartorius 2) rectus abdominus 3) rectus femoris 4) gracilis

Question 74

Surgical mortality in EVAR infected explant

Answer 74

10-30%

Question 75

Reinfection in EVAR infected explant

Answer 75

5-10%

Question 76

Selection criteria for open surgical technique

Answer 76