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Flashcards in Necrotizing Fasciitis Deck (17)
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1
Q

Epidemiology

A
  • mortality rate directly propotional to time of intervention
  • mortality rate increases with depth of primary site infection
  • incidence increasing (possible due to increase microb virulence or excessive antibiotic use)
2
Q

Classification

A
  1. Based on anatomy
    - eg. fournier’s gangrene (perineum)
  2. Depth of tissue infection
    - adipositis
    - fasciits
    - myositis
  3. Microbial source of infection
    - Type 1: polymicrobial (commonest, averagely 4 organism)
    - Type 2: monomicrobial
    - Type 3: Vibrio Vulfinicus
3
Q

Infective organism

A
  1. Polymicrobial
    - common: +ve cocci, -ve rods, anaerobes
    - less common: bacteroides, clostridium
    - rare: Clos. perfringes
    - usually immunocompromised
  2. Monomicrobial (Gram +ve)
    - GABHS +/- Staph aureus
    - associated with TSS
    - GABHS can survive and replicate in macrophage, escape antibiotics therapy
    - usually immunocompetent
    - MRSA commom in IVDU
  3. Vibrio vulfinicus (Gram -ve)
    - coastal community, exposure to warm sea water
    - fulminant course of disease, rapid spreading
4
Q

Risk Factors

A
  1. DM
  2. PVD
  3. Obesity
  4. Alcohol abuse
  5. IVDU
  6. Insect bites
  7. Surgery/Trauma
5
Q

Pathophysiology

A
  1. Inoculation to SC via trauma or perforated viscus
  2. Organism release endo and exotoxins
  3. Damage microvascular integrity, small perforating vessels thrombosis, tissue ischemia
  4. Impedes oxidative destruction by PMNCs, or antibiotic delivery
6
Q

Clinical Features

A

Early:

  1. Skin redness (100%) - later blackish, gangrenous
  2. Pain, disproportionate to appearance, beyond margins of erythema, rapidly progressive (98%)
  3. Swelling (92%)
  4. Fever (53%)

Late:

  1. Bullae (45%)
  2. Crepitus or skin necrosis (13%)
  3. Skin numbness

++Vibrio vulnificus: CVS collapse before skin changes occur

7
Q

X-Ray

A
  1. SC gas
  2. Soft tissue swelling
    - not sensitive (cannot rule out diagnosis if absent)
8
Q

CT Scan

A
  1. Fascial edema
  2. Fascial thickening (80% sensitivity)
  3. Abscess
  4. Gas formation
9
Q

MRI

A
  • most sensitive (100%) bt less specific (75%)

i. fascial thickening on T2
ii. hyperintense deep fascia, within muscles T2

10
Q

US

A
  • detect superficial abscess only

- not specific or sensitive for NF

11
Q

Laboratory Investigation

A

LRINEC

  1. CRP >150
  2. TWBC >15
  3. Hb <13.5
  4. Sodium <135
  5. Creat >141
  6. Glucose >10

> 6 predictive value for NF

12
Q

Culture and Sensitivity

A
  • No role for blisters or skin surface C/S

- Intraop biopsy: from interface between dead and living tissue

13
Q

Management

A
  1. Resuscitation
    - IV fluids (fluid loss from wound)
    - anti-pyretics
  2. Start empirical antibiotics
  3. Emergency wound debridement/amputation + tissue c/s
  4. Wound inspection after 24 hours (Rapidly progressive)
  5. Wound care
    - daily dressings +/- NPWT
    - wound closure

others:
++ hyperbaric O2 - controversial
++ latest: IVIG - for streptococcal NF

14
Q

Surgical Debridement

A
  1. 2 cm incision deep to fascia level:
    Operative findings:
    - dishwater foul smelling
    - tissue necrosis
    - lack bleeding
    - loss of normal resistance of fascia to finger dissection “probe test”
  2. Remove non-viable tissue (according to principle)
  3. Delayed primary closure/secondary intention
15
Q

Dressings

A
  1. VAC once infection is controlled
  2. Wet to dry dressings:
    - sodium hydrochloride, iodine, antibiotic solition has little benefits
  3. Definitive wound closure:
    - skin grafts
    - flaps
16
Q

Antibiotics

A
  1. Clindamycin - anaerobes, inhibits exotoxin GABHS
  2. Quinolones - excellent soft tissue penetration, gram negative
  3. 2 weeks course

empirical: penicillin
definitive:
- strep, clostridium (penicillin)
- imipenem (polymicrobial)
- vancomycin (MRSA)

17
Q

Prognosis

A
  • more frequent to develope systemic manifestation
  • 1 inch per hour
  • based on timing and adequacy of initial debridement