gangrene

Question 1

definition of gangrene

Answer 1

tissue necrosis, either wet with superimposed infection, dry (with dessication) or gas gangrene.

death of tissue from poor vascular supply and is a sign of critical ischaemia

dry is necrosis in absence of infection

wet - tissue death and infection (associated with discharge) occuring together

gas - subset of necrotizing myositis caused by spore-forming clostridial species.

Question 2

aetiology of gangrene

Answer 2

poor vascular supply

Tissue ischaemia and infarction,

physical trauma,

thermal injury,

inadvertent arterial injection, e.g. thiopentone and infection.

Gas gangrene iscaused by Clostridia perfringens.

Question 3

RF for gangrene

Answer 3

dm

trauma

PVD and leg ulcers

immunosuppression

steroids

malignancy

Question 4

pathology of gangrene

Answer 4

Tissue damage and ischaemia predispose to colonisation and proliferation of bacteria.

In the presence of an anaerobic environment, synergy between organisms occurs perpetuating the cycle of tissue damage and bacterial growth.

C. perfringens, C. novyi and C. septicum are gram-positive rod-shaped spore-forming saprophytes.

• They grow in the anaerobic environment of damaged tissue and produce exotoxins, e.g. a-lethicinase, which destroy the local microcirculation, cause necrosis, haemolysis and sepsis

Question 5

epidemiology of gangrene

Answer 5

gangrene common

gas gangrene rare

Question 6

sx of gangrene

Answer 6

pain with discolouration in the effected area, often the extremities or areas subject to pressure

tissues are black and may slough

dry - line of demarcation between living and dead tissue

gas - rapid onset of myonecrosis, muscle swelling, gas production, sepsis, and severe pain

Question 7

signs of gangrene

Answer 7

The painful area is usually the erythematous region around the gangrenous tissue, with the latter black because of haemoglobin breakdown products, dead and insensate

wet - tissue boggy, pus, strong odour from anaerobes

gas - spreading infection and destruction of tissues and muscle causes overlying oedema, discoloration and crepitus due to gas formation by the infection.

Question 8

ix of gangrene

Answer 8

blood - FBC, UE, glucose, CRP, blood culture

wound swab, pus/fluid aspirate

• microscopy
• gram stain
• culture
• sensitivity

XR of affected area - May show gas in the tissues formed by organisms.

Question 9

mx of gangrene

Answer 9

Surgical debridement and intensive supportive care +- amputation
broad spectrum abx - vancomycin and piperacillin

Question 10

abx for gas gangrene

Answer 10

IV benzylpenicillin sodium and clindamycin

Question 11

mx of ischemic gangrene

Answer 11

IV heparin
surgical revascularisation +- amputation
or if LE less than 2yrs - percutaneus transluminal angioplasty +- amputation
if viable extremity - thrombolytic therapy
if phlegmasia cerulea dolen - thrombolytic therapy

Question 12

what is phlegmasia cerulea dolen

Answer 12

severe DVT where blood cannot flow through vein - can lead to gangrene

Question 13

patient discussions with gangrene

Answer 13

life and limb threatening
recurrence is rare
may need further surgery
if ischemic gangrene - strongly advise smoking cessation

Question 14

monitoring for gas gangrene

Answer 14

can be very ill - need HDU or ITU
monitor for :
* lack of response to abx
* decline in resp
* haemodynamic function
* consider toxic shock if gp A strep infection

Question 15

complications of gangrene

Answer 15

sepsis
shock
AKI
haemolysis
loss of limb
DIC