Surg - Viva - Nec Fasc Flashcards
What is necrotising fasciitis
Fulminant bacterial infection of the deep fascia and subcut fat.
Different from cellulitis as that is at the superficial fascia and dermis
How is it different from cellulitis
Different from cellulitis as that is at the superficial fascia and dermis
Describe the pathophysiology
The organisms release exo and enotoxins and enzymes that cause rapid infection through fascial planes
extensive tissue damage
Subsequent interuption of microcirculation
–> vascular thrombossi and local necrosis/ischaemia of skin
Loss of sensation from superficial nerve destruction
Types
1 - polymicrobial
2 - Group A strep +/- S.aureus
3 - Gram neg monomicrobial (Vibrio)
4 - Fungal Candida
Describe the polymicrobial
Grm pos cocci and bacilli, gram neg and anaerobes
Usually more than 1 anaeoribc specia (clostridium, bacterioides)
Risk - DM, HIV, IVDU, alcohol
Assoc with chicken pox
Describe class 4
Fungal mostly in trauam patients, wounds and burns, and immnocomprimsed
Mortality 47%
Presentation of NG
Severe pain out of proprotion with the findings
PRECEDES the skin changes by 48 hours
Skin may loo normal
Progression - haeorrhagic bullae
Ulceraction
Nectrosis of skin
Thrombosis of capilary beds BEFORE skin changes
Latter - fulminant sepsis, shock, TSS (partiular in Group A strep) and MOF
Skin features
3 stages
1) Erythema wth tenderness extending beyond swelling
2) Formationof bullae and blisters, fluctuant skin
3) Haemorahhagiv bullae, crepitus, necrosis, gancrene
Ix of NF
Largely clincal.
Do not delay surery for radiology
Surgery - fascial necrosis with or without dead muscle
No resistnce to blunt disessection, no bleeding
Foul dishwater pus
Tests
Bloods - FBC, U&E, raised CK, low Ca. Coag (DIC)
Micro - bloood cultures in 20% of type 1, and 11-60% of type 2
Tissue samples and aspirates
Fungal culture in high risk
Histology to cofnrim fascial involvement
Radiology - MRI differentiates oedema from necrosis (T2)
USCT
Scoring system
Laboaratory Risk Indicator for NF (LRINEC)
> 6 PPV 92% NPV 96%.
8 PPV 93.4%
Features CRP >150 (4) WCC 15-25 (1), >25 (2) Hb 110-135 (1) < 110 (2) Na <135 (2) Cr >141 (2) Glucose >10 1
Tx
resus, supportive care
early exploration and debridements; delay is bad
Regular re-looks
empirical Abx - ben pen and clindoamycin (turns off toxin production)
If mixed - ceftriaxone
MRSA with vancomicin
IvIG
HBOT swith off toxin production in clostridal infection. Weak evidence in non-clostrial
How does IvIG work
Indixated in strep/staph NF
Induces antibody against exotoxin
Neutralises superantigens
Inhibits Membrane attack complex and complemetn
Opsoniation of GAS organsism
