Gangrene (CV) Flashcards
Define gangrene.
Complication of necrosis characterised by decay of body tissues.
What are the two major types of gangrene? (2)
- infectious gangrene (wet):
- necrotising fasciitis
- gas gangrene - Clostridium perfringes
- ischaemic gangrene (dry) - arterial or venous obstruction (PAD)
What is ischaemic gangrene (dry) caused by?
Peripheral artery disease (critical limb ischaemia) due to atherosclerosis (arterial obstruction) or venous obstruction
Compare peripheral artery disease (PAD) with Buerger’s disease (thromboangiitis obliterans). (2)
- PAD - leg pain with strenuous exercise, but not commonly associated with Raynaud’s phenomenon
- Buerger’s is a small and medium vessel vasculitis strongly associated with smoking and causes Raynaud’s phenomenon
What do we see on angiogram for Buerger’s disease (gangrene)?
Corkscrew-shaped collateral blood vessels
What are the types of infective gangrene? (2)
- necrotising fasciitis
- gas gangrene
Describe dry (ischaemic) gangrene.
Necrosis in absence of infection with atherosclerosis, thrombosis or vasospasm
Describe wet gangrene.
Tissue death and infection
Describe gas gangrene.
Susbet of necrotising myositis caused by spore-forming Clostridial species
Describe progressive bacterial (Meleney’s) synergistic gangrene.
Synergistic interaction between Staphylococcus aureus and microaerophilic streptococci (ileostomy/colostomy)
What is necrotising fasciitis (type of infective gangrene)?
Life-threatening infection of deep fascia causing necrosis of subcutaneous tissue
What is Fournier’s gangrene?
Necrotising fasciitis of the scrotum/vulva
What might gangrene result from?
Ischaemia, infection or trauma (or a combination of these processes)
What is the most common cause of gangrene?
Critically insufficient blood supply - often associated with diabetes and long-term smoking
What are the general clinical features of gangrene? (4)
- pain
- oedema/swelling
- skin discolouration (e.g. painful black tissue)
- feeling of heaviness in affected area
What are some clinical features specific to wet gangrene? (3)
- sudden onset of pain
- low grade fever and chills
- poorly demarcated necrotic area
What are some clinical features specific to ischaemic (dry) gangrene? (3)
- diminished pedal pulses and ABPI
- well demarcated necrotic area
- Hx of chronic claudication (pain in arms/legs when moving)
What are some clinical features specific to gas gangrene? (8)
- darkened skin
- crepitus - due to escaping gas
- infective area gives off distinct and potent smell
- may be able to visualise on radiograph
- rapid onset myonecrosis
- muscle swelling
- sepsis
- severe pain
What might you find on examination in gangrene? (4 + 3)
- painful area
- gangrenous tissue - black to due Hb breakdown products
- haemorrhagic blisters
- signs of systemic inflammatory response + sepsis
- wet gangrene - tissue boggy with pus and strong odour caused by anaerobe activity
- gas gangrene - spreading infection, destruction of tissues causing overlying oedema, discolouration, crepitus
- ischaemic gangrene - diminished pedal pulses and ABPI
What are some risk factors for gangrene? (8)
- diabetes mellitus
- atherosclerosis (ischaemic gangrene)
- smoking (ischaemic gangrene)
- drug and alcohol use
- renal disease
- malignancy
- trauma/abdominal surgery (infectious gangrene)
- contaminated wounds (infectious gangrene)
What are the first-line investigations for gangrene? (6)
- FBC
- comprehensive metabolic panel
- serum LDH - elevated if haemolytic anaemia
- coagulation panel - normal
- blood cultures - positive for infective organism
- serum CRP - elevated in necrotising fasciitis
What might FBC show in gangrene? (3)
Leukocytosis, haemoconcentration or anaemia
What might comprehensive metabolic panel show in gangrene? (4)
- low sodium
- metabolic acidosis
- liver derangement
- renal failure
What investigation would you do if infectious gangrene is suspected?
Blood cultures
How can you detect the presence and severity of arterial or venous obstruction in gangrene?
Doppler ultrasonography
What might plain x-ray show in gas gangrene?
May demonstrate gas in the soft tissues and/or indicate underlying osteomyelitis
How can you make a definitive diagnosis of gangrene? (2)
- surgical exploration
- skin biopsy
What are some differential diagnoses for gangrene? (7)
- Staphylococcal skin lesions (distinct pustules, blood cultures)
- erysipelas (recurrent pharyngitis, prodrome of pruritus and burning)
- cellulitis
- insect bites
- DVT
- polymyositis
- pyoderma gangrenosum
What is the 1st-line treatment for necrotising fasciitis awaiting MC&S?
- surgical debridement
- intensive supportive care
- empirical broad-spectrum Abx (vancomycin, tazobactam)
What is the 1st-line treatment for polymicrobial necrotising fasciitis? (5)
- intensive supportive care
- surgical debridement
- local irrigation with bacitracin-infused normal saline
- broad-spectrum IV Abx
- consider amputation
What is the 1st-line treatment for monomicrobial necrotising fasciitis? (6)
- intensive supportive care
- surgical debridement
- IV Abx
- IVIg (Streptococcal toxic shock)
- consider hyperbaric oxygen therapy
- consider amputation
What is the 1st-line treatment for gas gangrene? (4)
- intensive supportive care
- surgical debridement
- IV Abx (benzylpenicillin sodium, clindamycin)
- consider amputation
What is the 1st-line treatment for ischaemic gangrene? (5)
- IV heparin
- surgical revascularisation
- life expectancy <2y: percutaneous transluminal angioplasty
- viable extremity or phlegmasia cerulea dolens: thrombolytic therapy
- non-viable limb: amputation
In summary, how do you manage wet gangrene (necrotising fasciitis & gas gangrene)? (2)
- surgical debridement
- broad-spectrum Abx
In summary, how do you manage dry/ischaemic gangrene? (3)
- IV heparin
- surgical revascularisation
- amputation if non-viable
What are some complications of gangrene? (6)
- sepsis
- shock
- acute renal failure
- haemolysis
- loss of limb
- DIC
What are two key factors for improving outcomes in gangrene (life and limb-threatening)?
- early recognition
- aggressive Abx and surgical management
What is dry gangrene linked to?
Critical limb ischaemia & PAD
