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• >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:• 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 CA-MRSA 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: 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