Makindo Medical Notes

Medical and surgical emergency. Don't delay if diagnosis considered. Delay in diagnosis increases mortality. May need extensive surgery, reconstruction, and often amputation

About

• A deep infection with necrosis and damage to the dermis and subcutaneous tissue
• Can traverse the usual fascial layers which often limit infection spread.
• Caused by Gram-negative or Gram-positive anaerobic bacteria
• My be due to a small wound at the surface

Risks

• People with diabetes, those who inject drugs
• Haematological malignancy

Microbiology: polymicrobial and mixed

• Group A Beta haemolytic Streptococci
• Staph Aureus including MRSA
• Aeromonas hydrophilia (tropical)
• Vibrio Vulnifcus (tropical)
• Fungal infections can be seen
• Clostridium and gas formation

Classification

• Type 1: Mixed. Enterobacteriaceae and anaerobes. Seen in immunocompromised, diabetics and post-surgery
• Type 2: Streptococcal Strep pyogenes Lancefield Group A produces a superantigen that stimulates T cells which release cytokines that stimulate macrophages which cause tissue damage. Known as the "flesh-eating disease"
• Type 3: gas gangrene or clostridial myonecrosis related to recent trauma or surgery due to Clostridium perfringens

Clinical

• Severe pain and swelling over area affected
• Severe systemic symptoms and inflammatory response
• Centre of the lesion is anaesthetic due to nerve damage
• Gas may be found below the skin with crepitus
• Multisystem failure.

Laboratory risk indicator for NEC: LRINEC Score for Necrotizing Soft Tissue Infection

• CRP > 150 mg/L or 15 mg/dL +4
• WCC 15-25 +1 > 25 +2
• Na < 135 mmol/L +2
• Creatinine > 141 umol/l or 1.6 mg/dL +2
• Glucose > 180 mg/dL or 100 mmol/L +1
• A LRINEC score = 6 or more is a reasonable cut-off to rule in necrotizing fasciitis, but a LRINEC <6 does not rule out the diagnosis.
• Note: Use with caution, as the LRINEC Score has performed poorly in external validation MDCALC

Differential

• Toxic Shock syndrome
• Mucormycosis infection

Investigations

• ↑ WCC and ↑↑CRP
• U&E: May find AKI
• Hypocalcaemia may be seen

Management

• ABC as ever. Oxygenate. Support. IV fluids. Hyperbaric oxygen has been used especially with mixed growth if available.
• Call Surgeons: Start Antibiotics and Aggressive surgical management is the mainstay of treatment for necrotising fasciitis. If suspected an exploratory incision and inspection can sometimes be undertaken the debridement if confirmed. Studies show delayed surgery increases mortality rates. Plastic surgeons and/or the on-call polytrauma consultant are the preferred choice in the first instance. Specimens for MC&S and histology should be requested.
• Contact Emergency Microbiologist: usual regimen is Benzyl Penicillin 1.2g 4 hourly IV plus Clindamycin 600mg qds IV plus Gentamicin once-daily IV
• For Penicillin allergy: Clindamycin 600mg qds IV infusion plus Gentamicin once-daily IV