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MSRA Dermatology [3] > [15] Necrotising Fasciitis > Flashcards

[15] Necrotising Fasciitis Flashcards

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1
Q

What is necrotising fasciitis?

A

An uncommon but life-threatening infection, defined as a necrotising infection involving any layer of the deep soft tissue compartment

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2
Q

What parts of the deep soft tissue compartment can be affected in necrotising fasciitis?

A
  • Dermis
  • Subcutaneous tissue
  • Fascia
  • Muscle
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3
Q

How do organisms spread to cause necrotising fasciitis?

A

From subcutaneous tissue along the superficial and deep fascial planes

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4
Q

What facilitates the spread of bacteria in necrotising fasciitis?

A

Bacterial enzymes and toxins

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5
Q

What is the effect of deep fascial infection?

A
  • Vascular occlusion
  • Ischaemia
  • Tissue necrosis
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6
Q

What happens to superficial nerves in necrotising fasciitis?

A

They are damaged causing a characteristic localised anaesthesia

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7
Q

How are the causative organisms of necrotising fasciitis classified?

A

Into 4 types

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8
Q

What is Type 1 cause of necrotising fasciitis?

A

Polymicrobial infection with aerobic and anaerobic bacteria

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9
Q

Who is Type 1 necrotising fasciitis usually seen in?

A

Immunocompromised or patients with chronic disease

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10
Q

What is the causative organism in Type 2 necrotising fasciitis?

A

Group A streptococcus

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11
Q

Who does Type 2 necrotising fasciitis occur in?

A

Any age group and otherwise healthy individuals

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12
Q

What is the underlying cause of Type 3 necrotising fasciitis?

A

Gram -ve monomicrobial infection

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13
Q

What is a usual cause of infection Type 3 necrotising fasciitis?

A

Marine organisms after seawater contamination of wounds, fish fin/sting injuries and raw seafood consumption

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14
Q

What is an example of a marine organism that can cause Type 3 necrotising fasciitis?

A

Vibrio vulinficus

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15
Q

What causes Type 4 necrotising fasciitis?

A

Fungal infection

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16
Q

What are the risk factors for developing necrotising fasciitis?

A
  • Skin injury
  • Underlying conditions
  • Varicella zoster infection (in children)
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17
Q

What types of skin injury can lead to necrotising fasciitis?

A
  • Insect bite
  • Trauma
  • Surgical wounds
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18
Q

What underlying conditions can increase risk of necrotising fasciitis?

A
  • Alcohol abuse
  • IV drug abuse
  • Chronic liver or renal disease
  • Diabetes
  • Malignancy
  • Immunosuppression
  • TB
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19
Q

What is the most common type of necrotising fasciitis?

A

Type 1

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20
Q

What percentage of necrotising fasciitis cases are caused by Type 1 infections?

A

70-80%

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21
Q

Why is early diagnosis of necrotising fasciitis difficult?

A

It often looks like a superficial skin infection early on

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22
Q

When should you have a high index of suspicion for necrotising fasciitis?

A

When the patient is systemically unwell or has disproportionate pain

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23
Q

Although it can affect anywhere, what parts of the body does necrotising fasciitis usually involve?

A
  • Extremities
  • Trunk
  • Perineum
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24
Q

What is the usual time course for necrotising fasciitis?

A

Develops over a few days but potentially much quicker

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25
Q

In typical necrotising fasciitis development, what happens over days 1-2?

A
  • Local severe pain
  • Swelling and erythema
  • Poorly defined margins
  • No response to antibiotics
  • Systemic illness
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26
Q

Why does necrotising fasciitis cause only local pain, swelling and erythema initially?

A

The necrotising infection is deep and so not visible

27
Q

What features can distinguish necrotising fasciitis from cellulitis in the first 2 days?

A
  • Disproportionate pain
  • No response to antibiotics
  • Lymphangitis is rare
  • Systemic illness
28
Q

What symptoms of systemic illness can be seen in the first few days of necrotising fasciitis?

A
  • Malaise
  • Tachycardia
  • Fever
  • Dehydration
29
Q

What may be seen in days 2-4 of typical necrotising fasciitis?

A
  • Tense oedema beyond erythema
  • Possibly haemorrhagic bullae
  • Discoloured skin progressing to grey necrosed skin
  • Subcutaneous tissue feels wooden
  • Pain progress to anaesthesia
30
Q

What happens in days 4-5 of necrotising fasciitis?

A
  • Hypotension and septic shock

- Patient becomes confused and apathetic

31
Q

What is Fornier’s gangrene?

A

A rapidly progressing form of infective necrotising fasciitis of the perineal and genital regions leading to thrombosis of the small subcutaneous vessels and necrosis of the skin

32
Q

How is necrotising fasciitis diagnosed?

A

Clinically

33
Q

What is required if necrotising fasciitis is suspected clinically regardless of other test results?

A

Surgical exploration

34
Q

What can sometimes be seen and act as a diagnostic tool on plain x-ray?

A

Gas or bullae

35
Q

What macroscopic features can confirm necrotising fasciitis on surgical exploration?

A
  • Grey necrotic tissue
  • Lack of bleeding
  • Thrombosed vessels
  • ‘Dishwater pus’
  • Lack of resistance to finger dissection
  • Non-contracting muscles
36
Q

What test can help to identify necrotising fasciitis if the clinical picture is uncertain?

A
  • Blood tests
  • Bedside finger test
  • Microbiology
  • Radiology
37
Q

What blood tests can help to identify necrotising fasciitis?

A
  • Leukocytosis
  • Acidosis
  • Altered coagulation profile
  • Hypoalbuminaemia
  • Abnormal renal function
38
Q

What is a bedside finger test for necrotising fasciitis?

A
  • 2cm incision down to deep fascia under local anaesthetic
39
Q

What are the signs of necrotising fasciitis on bedside finger testing?

A
  • Lack of bleeding
  • Malodorous ‘dishwater pus’
  • Lack of tissue resistance to blunt dissection
40
Q

What microbiological tests can be useful for necrotising fasciitis?

A
  • Blood cultures

- Wound swab

41
Q

What radiological investigations can help to diagnose necrotising fasciitis?

A
  • Plain X-ray
  • CT
  • MRI
  • USS
42
Q

What can be seen on a CT or -ray in some cases of necrotising fasciitis?

A

Tissue gas

43
Q

What can be sometimes seen on MRI in necrotising fasciitis?

A

Extent of tissue involvement

44
Q

What can sometimes be seen on USS in necrotising fasciitis?

A

Subcutaneous gas

45
Q

Why is imaging not always useful in necrotising fasciitis?

A

There are often false negatives

46
Q

What are the differentials for necrotising fasciitis?

A
  • Cellulitis
  • Erysipelas
  • Pyoderma gangrenosum
  • Limb ischaemia or compartment syndrome
  • Deep vein thrombosis
  • Thrombophlebitis
  • Osteomyelitis
47
Q

What treatment for necrotising fasciitis is essential?

A

Early and aggressive debridement of involved tissue

48
Q

What are other important aspects of necrotising fasciitis management?

A
  • Resuscitation
  • Antibiotics
  • Post-debridement surgery
49
Q

Why may patients with necrotising fasciitis require resuscitation?

A

They are often shocked or haemodynamically unstable

50
Q

Where is it often appropriate to treat patients with necrotising fasciitis?

A

Intensive care

51
Q

What is important to ensure when surgically debriding necrotising fasciitis?

A

Adequate margins with no infected tissue remaining

52
Q

What must happen after initial debridement of necrotising fasciitis?

A

Wound monitoring and daily debridement of recurring infection

53
Q

When can necrotising fasciitis wounds be dressed?

A

Once the infection is controlled

54
Q

How are necrotising fasciitis wounds closed?

A

By secondary suturing with or without skin grafts

55
Q

What may assist healing of necrotising fasciitis wounds?

A

Vacuum assisted wound closing devices

56
Q

How should antibiotics be started in necrotising fasciitis?

A

Immediately start IV broad-spectrum at high doses

57
Q

What organisms should be covered by antibiotics for necrotising fasciitis?

A
  • Streptococci
  • Staphylococci
  • Gram-ve rods
  • Anaerobes
58
Q

What support is required in necrotising fasciitis?

A
  • Fluid

- Nutrition

59
Q

When should prophylactic treatment be given to patient contacts?

A

When there is GAS infection

60
Q

What prophylactic treatment should be given to all contacts of a person with GAS necrotising fasciitis?

A

Advice about symptoms and when to seek help

61
Q

When should prophylactic antibiotics be given to contacts of GAS necrotising fasciitis?

A
  • Neonates and mothers if either have invasive GAS
  • Close contacts with symptoms of localised GAS
  • Household if 2 or more cases of invasive GAS in 1 month
62
Q

What are some symptoms of localised GAS infection?

A
  • Sore throat
  • Fever
  • Skin infection
63
Q

What is the first choice antibiotic in necrotising fasciitis?

A
  • Penicillin V
64
Q

What are the potential complications of necrotising fasciitis?

A
  • Septic or toxic shock
  • Tissue necrosis
  • Nerve damage
  • Muscle necrosis
  • Skin grafting
  • Reconstructive surgery
  • Amputation

MSRA Dermatology [3] (26 decks)

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