Gangrene Flashcards
Describe what is meant by the term gangrene [1]
Where in the body does this commonly occur? [1]
Why does gangrene occur? [2]
Gangrene refers to the localised death of bodily tissue (i.e. necrosis).
This commonly occurs at the extremities (e.g. digits).
It can be due to a lack of blood supply or a serious infection (usually bacterial).
Describe the two types of gangrene? [2]
Dry:
- tissue is dry
- Usually evidence of shrunken, black, necrotic tissue.
- Often from ischaemia
Wet:
- tissue is wet.
- Usually evidence of oedema, ulceration, and exudate.
- Often due to a necrotising infection.
‘Gas gangrene’ is a specific type of necrotising infection, often due to the gas-producing bacteria []
‘Gas gangrene’ is a specific type of necrotising infection, often due to the gas-producing bacteria Clostridium perfringens.
Fournier’s gangrene - refers specifically to necrotising fasciitis of which body areas? [2]
Fournier’s gangrene - refers specifically to necrotising fasciitis of the perineum and scrotum.
Describe the different classifications of Necrotising soft tissue infections (NSTIs) with regards to their infective organisms
Type I:
- polymicrobial: typically mixed anaerobes & aerobes, on average four or more organisms
Type II:
- group A streptococcus (Strep. pyogenes +/- Staph. aureus)
Type III:
- Gram-negative monomicrobial infection.
- Typically associated with Vibrio species infection
Type IV:
- Fungal infection (typically Candida species, zygomycetes).
Which areas do type 1 and type 2 commonly affect? [2]
Type 1: perineum and trunk
Type 2: limbs
Describe the typical patient suffering from type 1 NSTI
Typically immunocompromised, diabetic and/or with multiple co-morbidities (peripheral vascular disease, obesity, chronic renal disease, chronic alcohol/drug abuse, HIV).
What is the typical type II NSTI patient? [1]
Type II NSTIs can occur in healthy, young, immuno-competent individuals
Which type of NSTI is associated with toxic shock syndrome?
Type 1
Type 2
Type 3
Type 4
Which type of NSTI is associated with toxic shock syndrome?
Type 1
Type 2
Type 3
Type 4
Describe the pathophysiology of NSTI [3]
Microbial invasion and enzyme release
- Initially there is microbial invasion within the superficial fascia (e.g. from minor trauma).
- The release of enzymes and endo/exotoxins results in rapid spread through the fascial planes.
Disruption to microcirculation
- Thrombosis of the small veins and arteries which pass up through the fascia results in ischaemia to the overlying skin.
- Early on, these skin changes are NOT obvious, despite extensive infection below.
Haemorrhagic bullae, ulceration & necrosis
- As the infection progresses skin necrosis becomes more evident. In the later stages, signs of profound sepsis and multi-organ failure may appear.
Describe a key clinical feature of NSTI [1v]
Disproportionate pain compared with physical findings is typical.
Pain often PRECEDES skin changes by 24-48hrs.
Skin changes of NSTIs typically occur in three stages.
Describe these stages [3]
Stage I
- Erythema, tenderness, swelling and warmth.
Stage II
- Bullae formation, blistering and fluctuation of the skin.
Stage III
- Haemorrhagic bullae, crepitus and tissue necrosis.
What is the gold standard for diagnosis of NSTIs? [1]
The gold standard is surgical exploration and tissue biopsy.
What is the name of the scoring system designed to distinguish between necrotising infections and other soft tissue infections (e.g. cellulitis)? [1]
LRINEC score
A score > [] suggests NSTI? [1]
A score greater than 6 is highly suggestive of an NSTI
