Necrotizing Fasciitis Flashcards
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
- Based on anatomy
- eg. fournier’s gangrene (perineum) - Depth of tissue infection
- adipositis
- fasciits
- myositis - Microbial source of infection
- Type 1: polymicrobial (commonest, averagely 4 organism)
- Type 2: monomicrobial
- Type 3: Vibrio Vulfinicus
3
Q
Infective organism
A
- Polymicrobial
- common: +ve cocci, -ve rods, anaerobes
- less common: bacteroides, clostridium
- rare: Clos. perfringes
- usually immunocompromised - 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 - Vibrio vulfinicus (Gram -ve)
- coastal community, exposure to warm sea water
- fulminant course of disease, rapid spreading
4
Q
Risk Factors
A
- DM
- PVD
- Obesity
- Alcohol abuse
- IVDU
- Insect bites
- Surgery/Trauma
5
Q
Pathophysiology
A
- Inoculation to SC via trauma or perforated viscus
- Organism release endo and exotoxins
- Damage microvascular integrity, small perforating vessels thrombosis, tissue ischemia
- Impedes oxidative destruction by PMNCs, or antibiotic delivery
6
Q
Clinical Features
A
Early:
- Skin redness (100%) - later blackish, gangrenous
- Pain, disproportionate to appearance, beyond margins of erythema, rapidly progressive (98%)
- Swelling (92%)
- Fever (53%)
Late:
- Bullae (45%)
- Crepitus or skin necrosis (13%)
- Skin numbness
++Vibrio vulnificus: CVS collapse before skin changes occur
7
Q
X-Ray
A
- SC gas
- Soft tissue swelling
- not sensitive (cannot rule out diagnosis if absent)
8
Q
CT Scan
A
- Fascial edema
- Fascial thickening (80% sensitivity)
- Abscess
- 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
- CRP >150
- TWBC >15
- Hb <13.5
- Sodium <135
- Creat >141
- 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
- Resuscitation
- IV fluids (fluid loss from wound)
- anti-pyretics - Start empirical antibiotics
- Emergency wound debridement/amputation + tissue c/s
- Wound inspection after 24 hours (Rapidly progressive)
- Wound care
- daily dressings +/- NPWT
- wound closure
others:
++ hyperbaric O2 - controversial
++ latest: IVIG - for streptococcal NF
14
Q
Surgical Debridement
A
- 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” - Remove non-viable tissue (according to principle)
- Delayed primary closure/secondary intention
15
Q
Dressings
A
- VAC once infection is controlled
- Wet to dry dressings:
- sodium hydrochloride, iodine, antibiotic solition has little benefits - Definitive wound closure:
- skin grafts
- flaps
