Necrotising Fasciitis Flashcards
What is necrotising fasciitis?
Necrotising fasciitis is a life-threatening subcutaneous soft-tissue infection that may extend to the deep fascia, but not into the underlying muscle.
Briefly differentiate between type 1 and type 2 necrotising fasciitis
Type I necrotising fasciitis is a polymicrobial infection with an anaerobe such as Bacteroides or Peptostreptococcus and a facultative anaerobe such as certain Enterobacterales or non-group A streptococcus.
Type II necrotising fasciitis is most commonly a monomicrobial infection with Streptococcus pyogenes (group A streptococci).
What are the risk factors for necrotising fasciitis?
- Diabetes mellitus
- Peripheral vascular disease,
- Immunocompromising conditions
- Chronic renal or hepatic insufficiency,
- Chickenpox or herpes zoster
- Intravenous drug use
- Certain medications (e.g. corticosteroids)
What are the signs of necrotising fasciitis?
- Tachycardia
- Tachypnoea
- Hypotension
- Crepitus
- Vesciles or bullae
- Grey discolouration of the skin
- Oedema
What are the symptoms of necrotising fasciitis?
- Anesthesia or severe pain over site of cellulitis
- Fever
- Lightheadedness
- Palpitations
- Nausea or vomiting
- Delirium
What investigations should be ordered for necrotising fasciitis?
- FBC
- U&E
- CRP
- Creatinine kinase (CK)
- Lactate
- Blood and tissue cultures
- Gram stain
- ABG
- Radiography, CT/MRI or ultrasound
- Surgical exploration
Why investigate FBC?
High WBC count is a non-specific finding that may be seen in any systemic infection or circulatory collapse. A low WBC count may be a sign of severe sepsis. If a spreading soft-tissue infection is present, necrotising fasciitis should be suspected.
Why investigate U&Es?
Hyponatraemia is a non-specific finding that may be seen in any systemic infection or circulatory collapse. If a spreading soft-tissue infection is present, necrotising fasciitis should be suspected.
Why investigate CRP?
Elevated CRP is a non-specific finding that may be seen in a range of systemic infections. If a spreading soft-tissue infection is present, necrotising fasciitis should be suspected.
Why investigate creatinine kinase (CK)?
A non-specific finding suggestive of systemic infection or circulatory collapse. If a spreading soft-tissue infection is present, necrotising fasciitis should be suspected.
Why investigate lactate?
A non-specific finding suggestive of systemic infection. Elevated serum lactate at admission appears to be associated with the presence of necrotising fasciitis.
Why investigate blood and tissue cultures?
Definitive bacteriological diagnosis is best made using tissue specimens obtained from surgical debridement and blood cultures.
Positive, may indicate polymicrobial or monomicrobial aetiology.
Why investigate using gram staining?
Staining of clinically affected tissue may provide early indication of causative organism(s). For example, small chains of gram-positive cocci suggest a streptococcal infection; clumps of large cocci suggest Staphylococcus aureus.
Why investigate using ABG?
May be obtained if there is concern for respiratory compromise. Helps determine patient’s respiratory status.
May show hypoxaemia and/ or acidosis.
Why investigate using radiography, CT/MRI or ultrasound?
Plain radiography, ultrasound, or CT/MRI (if available) may be obtained in all patients with suspected necrotising fasciitis, if clinically appropriate. The diagnosis should be strongly suspected if soft-tissue gas is visualised on radiological examination, which may also demonstrate abnormalities in the involved soft tissue.
