Necrotising Fasciitis Flashcards
What is necrotising fasciitis?
An uncommon but life-threatening infection, defined as a necrotising infection involving any layer of the deep soft tissue compartment
What parts of the deep soft tissue compartment can be affected in necrotising fasciitis?
- Dermis
- Subcutaneous tissue
- Fascia
- Muscle
How do organisms spread to cause necrotising fasciitis?
From subcutaneous tissue along the superficial and deep fascial planes
What facilitates the spread of bacteria in necrotising fasciitis?
Bacterial enzymes and toxins
What is the effect of deep fascial infection?
- Vascular occlusion
- Ischaemia
- Tissue necrosis
What happens to superficial nerves in necrotising fasciitis?
They are damaged causing a characteristic localised anaesthesia
How are the causative organisms of necrotising fasciitis classified?
Into 4 types
What is Type 1 cause of necrotising fasciitis?
Polymicrobial infection with aerobic and anaerobic bacteria
Who is Type 1 necrotising fasciitis usually seen in?
Immunocompromised or patients with chronic disease
What is the causative organism in Type 2 necrotising fasciitis?
Group A streptococcus
Who does Type 2 necrotising fasciitis occur in?
Any age group and otherwise healthy individuals
What is the underlying cause of Type 3 necrotising fasciitis?
Gram -ve monomicrobial infection
What is a usual cause of infection Type 3 necrotising fasciitis?
Marine organisms after seawater contamination of wounds, fish fin/sting injuries and raw seafood consumption
What is an example of a marine organism that can cause Type 3 necrotising fasciitis?
Vibrio vulinficus
What causes Type 4 necrotising fasciitis?
Fungal infection
What are the risk factors for developing necrotising fasciitis?
- Skin injury
- Underlying conditions
- Varicella zoster infection (in children)
What types of skin injury can lead to necrotising fasciitis?
- Insect bite
- Trauma
- Surgical wounds
What underlying conditions can increase risk of necrotising fasciitis?
- Alcohol abuse
- IV drug abuse
- Chronic liver or renal disease
- Diabetes
- Malignancy
- Immunosuppression
- TB
What is the most common type of necrotising fasciitis?
Type 1
What percentage of necrotising fasciitis cases are caused by Type 1 infections?
70-80%
Why is early diagnosis of necrotising fasciitis difficult?
It often looks like a superficial skin infection early on
When should you have a high index of suspicion for necrotising fasciitis?
When the patient is systemically unwell or has disproportionate pain
Although it can affect anywhere, what parts of the body does necrotising fasciitis usually involve?
- Extremities
- Trunk
- Perineum
What is the usual time course for necrotising fasciitis?
Develops over a few days but potentially much quicker
In typical necrotising fasciitis development, what happens over days 1-2?
- Local severe pain
- Swelling and erythema
- Poorly defined margins
- No response to antibiotics
- Systemic illness