Necrotising FASCIITIS NF

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

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

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)

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

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

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

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’

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