see also:

• peripheral vascular disease (PVD or PAD)
• vascular surgery
• West J Med. 2000 Jul; 173(1): 60–63. Chronic lower limb ischemia

• 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.

• 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)
    • rarely, the cause may be thrombosis of the aorta
  • arterial embolism (eg. from AF or abdominal aortic aneurysm (AAA)), trauma, or from peripheral aneurysms causing embolism
    • these can occur at any age

• patients with collateral circulation with peripheral vascular disease (PVD or PAD) who develop thrombosis or reconstruction (graft or stent) occlusion

• 2 main aims:
  • determine presence, time of onset and severity of the ischaemia
  • determine risk factors, past relevant interventions and to exclude possible differentials to limb ischaemia
    • PH of peripheral vascular disease (PVD or PAD) - intermittent claudication, rest pain, etc
    • past vascular interventions to the proximal arteries including recent diagnostic arterial catheterisations such as coronary angiography
    • AF
    • abdominal aortic aneurysm (AAA)
    • atherosclerosis risk factors - hypertension, diabetes mellitus, smoking, hyperlipidaemia
    • known atherosclerosis history - stroke (CVA), ischaemic heart disease (IHD), amputations, blood clots

• 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

• 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

• the shocked hypotensive patient especially in a patient with peripheral vascular disease (PVD or PAD)
• phlegmasia cerulea dolens
• acute compressive neuropathy

• trauma (eg. dislocation of the knee joint)
• aortic dissection
• abdominal aortic aneurysm (AAA)
• arteritis with thrombosis (eg. giant cell arteritis)
• HIV / AIDS arteriopathy
• hypercoagulable states causing thrombosis
• thrombosis of popliteal artery due to adventitial cyst or entrapment
• compartment syndrome

• 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.