Acute Limb Ischaemia

  • Acute limb ischaemia (ALI) defines the suddenness of onset, not severity
  • The severity of ischaemia may be absolute (no blood flow – a white, bloodless limb) or relative (acutely reduced blood flow but some colour, feeling and movement in the foot)
  • The symptoms and signs reflect the underlying cause and dictate the urgency of referral
  • ALI may be primarily due to:
    • Embolus into normal arteries (usually absolute ischaemia)
    • Thrombosis of a popliteal aneurysm (usually absolute ischaemia)
    • Thrombosis of existing disease (usually relative ischaemia)


Signs and Symptoms

  • Pain of sudden onset at rest or walking short distances (calf, thigh or entire limb)
  • Always affects the foot (calf pain with no symptoms in the foot is not typical of ischaemia)
  • Interferes with sleep/ worse with elevation of the limb / better with limb dependent

History and Examination


Relating to embolus:

  • Sudden onset of severe limb pain, numbness and paralysis
  • Underlying cause (eg. AF without anticoagulation; limb trauma)

Relating to thrombosis ("thrombosis-in-situ" or "acute on chronic ischaemia")

  • Known arteriopath / vascular risk factors
  • Pre-existing symptoms of peripheral arterial disease (intermittent claudication)
  • Sudden deterioration in claudication distance / rest pain
  • Known lower limb aneurysm (femoral or popliteal)

Absolute ischaemia

  • The "six P's": Pale (bloodless limb), Painful, Pulseless, Perishing cold, Paraesthaesia, Paralysis
  • Absent pulses on affected side with normal pulses on the other side suggest embolism
  • Atrial fibrillation – commonest cause of embolism
  • Loss of sensation, paralysis and muscle tenderness are signs of advanced ischaemia and need for emergency intervention

Relative ischaemia

  • Symptoms without the features of absolute ischaemia
  • Abnormal pulses in both legs
  • Doppler examination – absent or abnormal flow signals at ankle/foot

Differential Diagnoses

  • Many other causes of leg pain – the symptoms bulleted above are the key to diagnosis.
  • DVT causes leg swelling and sometimes blue discoloration, but hand-held Doppler examination shows good arterial flow signals at the foot/ankle.

Red Flags

  • Bloodless limb
  • Rest pain and altered sensation


  • Absolute ischaemia: None – Emergency referral
  • Acute onset of relative ischaemia: None – Emergency referral


  • Absolute ischaemia:
    • Emergency referral to the vascular service
    • Analgesia
  • Relative ischaemia
    • Risk factors modification:
      • Smoking advice
      • Diabetic review
      • Statin therapy
      • Blood pressure control
      • Antiplatelet therapy
    • Urgent outpatient referral to the vascular service


Referral Criteria

  • Absolute or relative ischaemia of acute onset

Referral Instructions

  • Absolute ischaemia immediate via Emergency Department or on call general surgical registrar
  • For discussion with a consultant ring switchboard and ask for vascular surgeon of the week

Relative ischaemia –urgent referral for outpatient appointment

  • Referral to vascular specialist
  • e-Referral service selection:
    • Specialty: Surgery - Vascular
    • Clinic Type: Not otherwise specified
    • Service: DRSS-Northern-Surgery Vascular- Devon CCG- 15N

Referral Forms

DRSS referral form

Supporting Information

Pathway Group

This guideline has been signed off by the Northern Locality on behalf of NEW Devon CCG.

Publication date: September 2015


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