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
The LRINEC score is based off which measurable factors? [6]
CRP
WCC
Hb
Na+
Creatinine
Glucose
A score > [] suggests NSTI? [1]
A score greater than 6 is highly suggestive of an NSTI
What is the overall mangement plan for NSTI? [2]
Management
1. urgent surgical referral debridement
2. intravenous antibiotics
Describe the Abx treatment given to NSTI patients
Antibiotics should be perceived as an adjunct to surgical debridement. Broad-spectrum antibiotics should be initiated without delay according to Trust guidelines. Commonly used agents include:
- Tazocin (piperacillin & tazobactam)
- Meropenem
- Clindamycin - particularly useful at ‘switching off’ exotoxin production.
- Linezolid - similarly inhibits exotoxin production.
NSTI:Type 2 is caused by []
PassMed
type 2 is caused by Streptococcus pyogenes
Which type of gangrene is commonly associated with chronic ischaemia?
Dry gangrene is due to prolonged ischaemia (infarction) or inadequate oxygenation or lack of blood flow. Ischaemia affecting proximal blood vessels usually affects the lower limbs. Ischaemia of the peripheries may cause gangrene of fingers and toes.
What are causes of chronic ischaemia causing gangrene? [2]
Peripheral arterial disease:
- due to atherosclerosis.
Venous insufficiency:
- The veins may fail to clear blood from the tissues because of valve dysfunction (varicose veins) and obstruction from deep venous thrombosis (DVT) or thrombophlebitis.
What are the different ABI scores for mild, moderate and severe arterial disease? [3]
- ABI 0.8-1.3 is normal when the pressure in the lower limbs is the same or greater than the upper limbs.
- ABI 0.5–0.8indicates mild to moderate arterial disease.
- ABI >0.5 indicates severe arterial disease.
Treatment of gangrene varies depending on location and cause but is centred around radical surgical debridement +/- amputation. Surgical procedures may also include what? [4]
- Removal of embolus or thrombus
- Balloon catheterisation or stent
- Arterial or venous bypass surgery
- Hyperbaric oxygen treatment.
