Necrotising fasciitis Flashcards
Another name for NF
Flesh-eating infections
Introduction to NF
Rapidly progressive severe infection of the fascia with secondary necrosis of the subscutaneous tissues
severe disease of sudden onset that spreads rapidly
Infections difficult to recognize at early stages, but rapidly progresses
Most commonly affected areas
Limbs (extremities)
perineum
genitals
Pathophysiology
Infection enters the body through a break in the skin such as ‘cut’ or ‘burn’
Trauma is the usual cause of infection- IV drug injection, insulin injections, animal & insect bites (portal of entry for infections)
Risk factors
- poor immune function with diabetes (immunosupression)
- obesity
- Alcoholism & smoking
- cancer/chronic systemic disease
- IV drug use
Symptoms
- unusual pain/pain out of proportion
- fever (often absent)
- vomiting
- severe pain
- red/purple skin in affected area
Signs of NF
- Pink/orange-staining/purple
- edema beyond the area of erythema
- crepitus- formation of gas inside
- skin blistering- hemorrhagic bullae
- greyish drainage “dishwater pus”
- focal skin gangrene (late sign)
- shock, coagulopathy, multiorgan failure
Types of NF
- Polymicrobial (80%)
- mixed infection: perineum, trunk & postoperative wounds
- non group A strep with anaerobes/clostridial/enterobacteriaceae (e.coli, pseudomonas) - Monomicrobial (20%)
- Group A strep/MRSA
- young, common in extremities without comorbidities - Type 3
- Gram-negative rods (Vibro vulficus) after a minor trauma
- associated with chronic liver & kidney disease, diabetes, steroid therapy) - Type 4 (rare)
- fungal infection (Aspergillus zygomycetes)
Clinical stages of NF
It is a ‘clinical diagnosis’
stage 1
- fever, eryhthema, edema, warm skin & tenderness
stage 2
- blisters & bullar formation
stage 3
- anaesthesia/hypoaethesia, crepitus, tissue necrosis, hemorrhagic bullae (ulceration)
Clinical features
NF & Left calf fasciotomy (involve muscle & fascia)
- liberal fasciotomy (longitudinal incision made on the medial & lateral aspect of leg)
- incise the deep fascia also-> swollen muscle prolapse outside)
Meleny’s gangrene (ant abdominal wall)
- post-op synergistic gangrene
- polymicrobial in nature
- “radical wound debridement” for the laparotomy wound
Fournier’s gangrene (skin scrotum)
- infection from perineum-> scrotal skin-> skin of anterior abdominal wall
Investigations of NF
LRINEC (Laboratory Risk Indicator for NF) Scoring system-> 6 parameters
> 8: severe- bad prognosis
6-8: moderate
<8: good- good prognosis
CRP (mg/L) >150-> 4 points
WBC count (x103/mm3)
- <15: 0 points
- 15-25: 1 point
- >25: 2 points
Hemoglobin (g/dl)
- >13.5: 0 points
- 11-13.5: 1 point
- <11: 2 points
Sodium (mmol/l):
<135-> 2 points
Creatinine (umol/l):
>141-> 2 points
Glucose (mmol/l):
>10-> 1 point
Investigation for NF
Gold standard for diagnosis: surgical exploration in the setting of high suspicion
Doubt: small incision made into affected tissue-> if finger easily seperates the tissue along the fascial plane-> “Finger swipe test”
others:
1. wound swab: for C & S- confirm microorganisms-> decide Ab
2. CT scan:
- fascial thickening
- edema
- abscess formation
- subcutaneous gas
Treatment of NF
- IV fluid, fresh blood transfusion
- Investigations: hematocrit, serum creatinine, blood & pus culture
- electrolyte mx
- ab
- catheterisation & monitoring of urine output hourly
- control of diabetic
- oxygen, ventilator, dopamine, dobutamine
- radical wound dissection/debridement
- vacuum assisted dressing
- hyperbaric oxygen
- split skin graft (large area-> mesh graft)
Treatment for NF
Usually treated with surgery to remove the infected tissues-> IV Ab
delays in surgery-> high death risk (25-35%)
Treatment for NF
Radical wound excision of gangrenous skin & necrosed tissue at repeated interval
after several wound debridement-> vacuum-assisted dressing is better
hyperbaric oxygen given in high-pressure chamber with 100% o2 in 2-3 atmospheric pressure
- reduces mortality 10-20%
- bactericidal
- promote the neutrophil function
when patient recovers with healthy granulation tissue-> split skin graft OR large area-> mesh graft (meshing of SSG)
MORTALITY : 30-50%
Key for successful outcome
1. early diagnosis
2. immediate surgical intervention
