Gangrene Flashcards
Define gangrene?
Tissue necrosis , either wet superimposed infection, dry or gas gangrene- due to poor vascular supply
what is dry gangrene?
necrosis in the absence of infection ( ischaemic gangrene)
what is wet gangrene?
tissue death and infection
what is gas gangrene?
subset of necrotising myositis caused by spore-forming clostridial species
what is necrotising Fascilitis?
a life-threatening infection of deep fascia causing necrosis of subcutaneous tissue
describe the aetiology of gangrene?
tissue ischaemia and infarction ( critical limb ischaemia)
physical trauma
thermal injury
gas gangrene is caused by clostridium perfinigens
outline the aetiology of necrotising fascitis?
usually poymocirobial involving streptococci, staphyococci, bacterioides and coliforms
what are the risk factors for gangrene?
Diabetes
Atherosclerosis (ischaemic gangrene)
Smoking (ischaemic gangrene)
Peripheral vascular disease
Renal disease
Drug/alcohol abuse
Leg ulcers
Malignancy
Immunosuppression
Steroid use
Puncture/surgical wounds (infectious gangrene)
Trauma (infectious gangrene)
summarise the epidemiology of gangrene and necrotising fasciitis?
gangrene- relatively common
necrotising fasciiitis and gas gangrene- RARE
what are the presenting symptoms of gangrene?
pain
discolouration of affected area- black
often areas extremities or areas subject to high pressure
gas gangrene- rapid onset of myonecrosis, muscle swellingl ,
what are the symptoms of necrotising
pain
what are the signs of necrotising gangrene?
painful area- erythematous region around gangrenous tissue
gangrene tissue- BLACK because of haemoglobin breal down products
wet gangrene- tissue becomes boggy with associated pus and strong odour caused by the activity of anaerobes
gas gangrene- spreading infection and destruction tissues causes overlying oedema
diminished pedal pulses and ankle- brachial index ( ischaemic gangrene)
May have lowgrade fever and chills
what are the appopriate investigations for gangrene?
bloods
wound swab, pus/ fluid aspirate MC and S
x ray of affected area- may show gas produced in gas gangrene or indicate underlying osteomyelitis
CT or MRI of affected site- may reveal abscess formation or oedema of thickening of fascia
doppler/ultrasonography- may indicate presence and severity of arterial/ venous obstruction
what bloods are needed to investigate gangrene and interepret the results?
FBC (leukocytosis and anaemia)
met panel (may have met acidosis, liver deragement and renal fail)
U&Es
LDH – elevated with haemolytic anaemia (common in gas gangrene)
Glucose
CRP – elevated
blood culture
