Necrotising Fasciitis
• is essentially a ‘severe inflammation of the muscle sheath that
leads to necrosis of the subcutaneous tissue and adjacent
fascia, that is difficult to diagnose early and even more
difficult to manage effectively.
Epidemiology and microbiology of
NF
• Incidence in U.K. = 0.24 to 0.4 per 100 000 adults
• Incidence in Canadian children,
• GAS NF was 0.21 per 100 000
• NonGAS NF 0.08 per 100 000
Types
Risk factors for NF
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>50 years of age
Diabetes mellitus
Peripheral vascular disease
Intravenous drug use
Alcoholism
Immunosuppression
Obesity
Pathogenesis
• Type1 :
• slower process, evolving over days.
• following complicated abdominal surgery, ischiorectal or perineal
abscesses
• gut flora breaches the mucosa, entering tissue planes
• Clostridium septicum or C. tertium points to an intrabdominal
focus
• C. sordellii is more associated with gynaecological pathology
or black tar heroin skin-popping
GASNF and GAS toxic shock
syndrome (STSS)
• 50% of type II NF cases are associated with STSS.
• STSS is an exotoxin-driven disease that significantly increases
the mortality of streptococcal NF alone from <40% to 67%
with up to half of patients needing amputation
Clinical diagnosis of NF
• Hx:
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minor trauma
insect or human bites
recent surgery
skin infection or ulcers
injection sites and
illicit intravenous drug usage
Many cases, however, remain idiopathic
• Hx:
• foreign travel >>> resistant or unusual organisms
• trauma involving soil contamination >>> fungal
• Raw seafood ingestion or wound exposure to seawater >>> Vibrio
spp.
• tonsillitis, impetigo, or recent non-steroidal anti-inflammatory
agent (NSAID) >>> streptococcal infection
Clinical diagnosis of NF
• Temperature: GASNF higher than synergistic
• 20% have influenza-like symptoms characterised by fever and
myalgia, severe pain, nausea, vomiting and diarrhoea
• Early diagnosis is difficult, especially in children, easily
misdiagnosed as muscle strains, viral illnesses, gastroenteritis,
‘allergic rash’ ,thrombosis, sprain or exacerbation of gout.
Clinical diagnosis of NF
• severe pain precedes skin changes by 24 to 48 h in >97.8% of
patients
• Mild erythema, cellulitis or swelling overlying the affected
area.
• lymphangiitis and lymphadenitis are rare.
• tender area >> smooth, swollen area of skin with distinct
margins progressing to dusky blue/purple, ‘bruising’
violaceous plaques, and finally full thickness necrosis with
haemorrhagic bullae
Radiology
• US findings correlate reasonably well with histological fat
changes in NF
• T2-weighted images on MRI are probably the best radiological
adjunctive investigation, but are more sensitive than specific
Labs
• Blood cultures are positive in 11 to 60% of patients with
GASNF
• Haemoglobinuria is common in GASNF
• Blister fluid is often sterile.
• Tissue biopsy is the investigation of choice for stain and C/S
• Disseminated intravascular coagulation and thrombocytopenia
are common
Labs
• A rapidly falling haemoglobin with stable haematocrit
• Leucocyte count is less helpful for diagnosis
• ARF
• CRP levels of >16 mg/dL, with a sensitivity of 89% and
specificity of 90%, have been reported
• Raised serum creatinine kinase (CK) indicates myositis or
myonecrosis
Labs
• CK levels of 600 U/L gave a sensitivity of 58% and a specificity
of 95% for cases of NF.
• 30% hypocalcaemic
• Hypoalbuminaemia and hyponatraemia
• high serum lactate with severe metabolic acidosis
The LRINEC (Laboratory Risk Indicator
for Necrotising Fasciitis)
The LRINEC (Laboratory Risk Indicator
for Necrotising Fasciitis)
• A score of 6 >> raises the suspicion
• A score 8 >> ‘strongly predictive’ of NF
• Predict mortality
Histopathology
• Deep incisional biopsies are more useful than punch biopsies
• Biopsy should include the advancing edge and central necrotic
areas
• Histological examination reveals underlying thrombi, necrosis,
polymorphonuclear infiltrate, microorganisms, and vasculitis.
• Gram staining is important, since a paucity of leucocytes in the
presence of Grampositive cocci may be seen in GASNF or CAMRSA due to leucocidin mediated destruction of WBCs.
Management
Surgical
• Prompt diagnosis
• Aggressive surgery removes the source of infection and toxins
• (VAC) dressing]with a continuous pressure of 40 to100 mmHg
is useful for wound coverage and encourages granulation
• the tissue oxygen tension can be measured with a probe using
transcutaneous soft tissue oximetry. lower in NF than cellulitis
Role of hyperbaric oxygen
(HBO)
• HBO switches off a-toxin production from Clostridium spp
• increase the bactericidal action of neutrophils
• Decrease mortality to 12%
Antibiotics
• Broad-spectrum empirical therapy covering most types of NF
• Then >> based on culture data.
• Penicillin: sensitivity? Cell wall action ?
• Clindamycin: switching off exotoxin production even in
stationary phase organisms
Empirical protocol
• I.V. clindamycin 1.2 to 1.8 g six-hourly with I.V. imipenem 0.5
to 1 g six-hourly.
• IF MRSA : I.V. linezolid 600 mg BID or daptomycin 6 mg/kg
may be added in preference to vancomycin
• For Vibrio spp. >> doxycycline 100 mg twice daily plus
intravenous ceftazidime 2 g eight-hourly is recommended
I.V.I.G
• IVIG may
• promote clearance of GAS by the immune system
• neutralise streptococcal superantigens
• act as an immunomodulatory agent
• contraindication
• selective IgA deficiency
• history of anaphylaxis with immunoglobulins.
• 2 g/kg, with the option of a second dose if necessary
after 24 h. rate of 20 mL/h, increasing incrementally
after 10 min to a maximum of 160 mL/h.
prognosis
• Bad prognostic factors:
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Not type 1
myonecrosis or myositis
STSS
High serum lactate combined with low sodium
Late operation
% BSA
Acidosis
Peripheral vascular disease
Advanced age
Other comorbidities
Antimicrobial prophylaxis for
contacts of GASNF
• 27% of household contacts may be GAS carriers (200 times
more likely to occur)
• CDC, do not recommend routine testing for GAS colonisation
or administration of chemoprophylaxis to household contacts.
• UK Health Protection Agency in 2004, recommend prophylaxis
to mothers and babies if either was infected during the
neonatal period
• Household contacts should be informed about the clinical
manifestations of pharyngeal and GAS infection
Patient information and
support
Patient information and
support