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R9 > Chapter 47 - Vascular graft infections > Flashcards

Chapter 47 - Vascular graft infections Flashcards

1
Q

Rate of graft infections in general

A

0.2-5%

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2
Q

Early infection rate < 30d

A

1-2%

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3
Q

Graft infections are more likely in:

A

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

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4
Q

Rate of OAAA infection and EVAR infection

A

0.2% for both

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5
Q

Rate of bare metal stent infection

A

< 0.1%

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6
Q

Early vs late infection defined by

A

4 months

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7
Q

Szilagyi class

A

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

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8
Q

Bunt’s class

A

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

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9
Q

Early infection more likely with:

A

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

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10
Q

Late infections more likely associated with:

A

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

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11
Q

Elek + Conen 1957 discovered…

A

Discovered that single braided silk reduces inoculum required for inrection

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12
Q

Risk of infections factors:

A

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

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13
Q

Pathogenesis of graft infection

A

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

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14
Q

Bacteria adhere to polyester compared to PTFE

A

polyester 10-100x more easily than PTFE

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15
Q

Gram + make this to increase adherence

A

extracellular glycocalyx (mucin)

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16
Q

Incorporation of graft impaired by:

A

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

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17
Q

Source of infection to graft:

A

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

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18
Q

Reoperation wound has bacteria culture positive in:

A

10-20%

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19
Q

Thrombosed graft has bacteria culture positive in

A

50-70%

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20
Q

Pseudoaneurysm at anastamotic sites has bacterial culture in

A

80%

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21
Q

Rate of GEE/GEF after aortic graft

A

0.4-2%

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22
Q

Things that impair host defense

A

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

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23
Q

Most prevalent pathogen in infected grafts

A

Staph aureus 25-50%

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24
Q

Growth negative cultures common with these organisms

A

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

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25
Q

Gram negative bacteria characteristics

A

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

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26
Q

Fungal and myobacterium characteristics

A

rare, only in immunocompromised or have ongoing infection elsewhere

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27
Q

MRSA rate in general population

A

2%

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28
Q

MRSA rate in LTC

A

23-49%

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29
Q

Prevention of graft infection

A

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

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30
Q

Routine rifampin on infections

A

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

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31
Q

Prophylactic antibiotic choice

A

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

32
Q

Prophylactic antibiotics for dental, colonoscopy and cystoscopy

A

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

33
Q

Rate of positive blood culture in graft infection

A

< 5%

34
Q

Diagnostic criteria for CT for infection

A

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

35
Q

When is gas around graft abnormal

A

After 2-3 months post-op

36
Q

Best use for ultrasound in ruling out infection

A

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

37
Q

MRI better than CT in infection for:

A

distinguish perigraft fluid vs fibrosis

38
Q

WBC scan radionuclide types

A

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

39
Q

When is WBC scan not useful

A

within 3-6 months post-op

40
Q

Ways to identify infection

A

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

41
Q

Culture techniques

A

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

42
Q

When is it ok to preserve graft in infections

A

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

43
Q

Organisms that cannot have graft preservation if concurrent sepsis

A

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

44
Q

Technique for graft preservation

A

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

45
Q

Deciding whether to do concurrent reconstruction

A

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

46
Q

Graft excision from aorta - principle

A

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

47
Q

Improvements in recent decades

A

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

48
Q

Patency of Ax-unifem at 6 months

A

94%

49
Q

Patency of Ax-unipop at 6 months

A

42%

50
Q

Who developed NAIS

A

Clagett 1993 Nevelsteen 1995

51
Q

Risk of calf compartment in SFV harvest after previous GSV harvest

A

12%

52
Q

Risk of venous insufficiency after SFV harvest

A

15%

53
Q

Pantaloon technique for aortic sizes:

A

18-26 mm

54
Q

Aortic sizes > this will need ex situ reconstruction

A

28 mm

55
Q

Benefit of NAIS over ex situ

A

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

56
Q

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

A

primary 81% secondary 91% amputation free 89%

57
Q

NAIS mortality

A

10%

58
Q

NAIS 5 year survival

A

52%

59
Q

Contraindication to NAIS

A

1) GEE/GEF 2) virulent Gram -

60
Q

Risk factors for stenosis after NAIS:

A

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

61
Q

Recurrent infection in Abx-soaked graft

A

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

62
Q

When to use abx-soaked graft

A

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

63
Q

Principles of operating on graft infection

A

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

64
Q

Who first used cryografts

A

Kieffer 1993

65
Q

1st gen Allograft 3 year rate of aneurysm/dilation

A

17%

66
Q

1st gen Allograft 3 year rate of stenosis/occlusion

A

20%

67
Q

Principle of using allograft

A

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

68
Q

Principles of antibiotics therapy

A

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

69
Q

Antibiotics in treating MRSA

A

Daptomycin 6 mg/kg daily

70
Q

Pseudomonas antibiotics coverage

A

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

71
Q

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

A

1) amox clav 2) fluoroquinolone

72
Q

Antibiotic bead ingredient

A

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

73
Q

Muscle flaps possible

A

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

74
Q

Surgical mortality in EVAR infected explant

A

10-30%

75
Q

Reinfection in EVAR infected explant

A

5-10%

76
Q

Selection criteria for open surgical technique

A
77
Q
A

R9 (200 decks)

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