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limb_ischaemia

acute limb ischaemia

introduction

  • acute limb ischaemia is a time critical condition which requires rapid recognition, assessment and management to save the limb and perhaps the patient's life.
  • it is not an uncommon cause of diabetic ketoacidosis (DKA) and in this scenario is often over-looked with dire consequences
  • it is characterized by a rapid decrease in limb perfusion which usually produces new or worsening symptoms or signs, and often threatens limb viability.
  • local blood flow = (arterial pressure - venous pressure) / arterial resistance
  • ischaemic inflammation produces tissue oedema (and potentially, compartment syndrome) which increases venous pressure, compresses arteries increasing resistance and reducing arterial pressure which is further exacerbated by sympathetic drive being activated causing further vasospasm creating a vicious cycle of deterioration1)

aetiology

acute - usually presentation within hours

  • this may be due to either:
    • thrombosis in patients lacking collateral circulation
      • this is the cause of 85% in those aged 65yrs and over (the other 15% being embolism)
    • arterial embolism (eg. from AF or abdominal aortic aneurysm (AAA)), trauma, or from peripheral aneurysms causing embolism
      • these can occur at any age

acute on chronic - usually delayed presentation over days

clinical assessment

history

examination

remember the 5 P's

  • Pain - time of onset, variation over time, location, intensity
  • Pulselessness - absence of pedal pulses suggests acute limb ischaemia which can be confirmed on Doppler USS, and measurement of ankle-brachial index (ABI)
  • Pallor (may be absent if collaterals present, and instead may have ischaemic rubor)
  • Paraesthesiae - if more than just in the toes, suggests limb viability is becoming critical
  • Paralysis - if present suggests probable non-viable limb
  • Prostration is Pratt's 6th P - hypotension and shock

assessing severity - Rutherford's categories of severity

  • category I: no sensory loss and no muscle weakness
  • category IIa: paraesthesiae confined to toes or not present suggests limb is viable and potentially salvageable
  • category IIb: more extensive paraethesiae with rest pain and only mild-moderate muscle weakness, but perhaps tender muscles and pain on passive movement suggests advanced acute limb ischaemia which may still be salvageable with immediate revascularisation
  • category III: profound anaesthesia and paralysis indicate major tissue loss and nerve damage which is probably irreversible and require amputation

is it really arterial ischaemia?

conditions mimicking acute limb ischaemia
other causes of arterial ischaemia

initial Mx in ED

  • iv access, FBE, U&E, glucose, clotting profile, CK
  • ECG
  • early vascular surgical consult is imperative
  • early anticoagulation with iv heparin is usually indicated to prevent extension of thrombosis
  • rapid confirmation with Doppler USS and/or CT angiography may be indicated
  • category I and IIa patients can usually have angiography to decide further Mx such as:
    • catheter directed thrombolytic Rx
    • percutaneous aspiration thrombectomy (PAT) +/- thrombolysis
    • percutaneous mechanical thrombectomy (PMT) +/- thrombolysis
  • category IIb patients will usually need immediate assessment for revascularisation procedure
    • 10–15% of patients’ limbs thought to be salvageable ultimately require major amputation
  • category III patients will generally require amputation or palliation depending upon pre-existing co-morbidities and likelihood of survival from surgery if presentation is severely delayed.

references

limb_ischaemia.txt · Last modified: 2019/08/28 15:31 (external edit)