1. Necrotising FASCIITISNF

2. Background NF is a rare and severe bacterial soft- tissue infection
About 500 cases per year in the UK
Responsible bacteria: mainly Group A Streptococci but can be a mixed infection
Infection advances very quickly and causes widespread necrosis of fasciae
High mortality if left untreated

3. TYPES OF NF Many different types of bacteria can cause NF:-
Type 1 (polymicrobial): caused by non-GAS bacteria and occurs mostly after surgical procedures or in patients with predisposing factors such as diabetes
Type 2 (monomicrobial): caused by GAS bacteria and Staphylococcus aureus
GAS: Group A Streptococci

4. RISK FACTORS
Most patients with NF present with comorbidities that may affect ability to fight infection
These include diabetes, peripheral vascular disease, cirrhosis, impaired kidney function, leukaemia and pressure sores
Some conditions may promote development of NF
These include: recent surgery, alcohol and drug abuse, traumatic injury and use of monoclonal antibody drugs (e.g. Avastin)

5. Pathology
Any site of the body can become infected but most commonly: lower extremities, abdomen, perianal area, groin and postoperative sites
Bacteria penetrate subcutaneous tissue and migrate into fasciae, soft tissue and muscle
Bacterial toxins accumulate producing subcutaneous gas and crepitus
Tissues start to die, deprived of oxygen, as circulation ceases
Bacterial toxins and enzymes facilitate spread of organisms resulting in deep-seated infection

6. Clinical Presentation
Symptoms often start within hours after injury: nausea, fever, diarrhoea, dizziness and severe pain
In hours to days: loss of consciousness, necrosis of tissues, dyspnea, hypotension and fatal shock syndrome
In 2-4 days (if untreated): formation of ulcers, blisters, black spots and bullae. Skin becomes grey. There may be anaesthesia of superficial layers due to destruction of nerves
Patient rapidly deteriorates and septicaemia ensues

7. DiAGNOSIS
Very difficult to diagnose in early stages and can be confused with other diseases e.g. cellulitis, sciatica, deep vein thrombosis
Intense fever may eliminate a diagnosis of cellulitis etc.
Patient may deteriorate rapidly despite treatment with antibiotics which may be suggestive of NF
Crucial to diagnose NF quickly because delay may lead to disease progression and a high risk of mortality

8. USEful investigations
There are no definitive diagnostic tests
Blood tests: raised C-reactive protein concentration occurs early in infection
Laboratory Risk Indicator for NF: most accurate diagnostic scoring system
Blood cultures for further antibiotic treatment
Imaging to detect subcutaneous gas production: MRI scans, CT scans and Ultrasound
Surgical intervention: ‘Finger test’

9. Medical management
Initial: iv fluids, supplemental oxygen, cardiac monitoring and assisted ventilation
Administration of a mixture of broad spectrum antibiotics e.g. Penicillin and Clindamycin
Debridement: wide and deep incisions revealing skin edges that are healthy, bleeding and free from necrosis
Amputation: 26% of extremity NF cases
Skin grafting for wound care and reconstruction