Arterial emergencies and aortic disease

Acute limb ischaemia

Overview and approach

Acute arterial occlusion threatens limb viability and requires immediate vascular review.

  • Definition: sudden decrease in limb perfusion, symptoms under 2 weeks. Causes: embolism (AF, cardiac source, aneurysm), thrombosis of native artery or graft/stent, trauma, popliteal aneurysm thrombosis, dissection (2)(3).
  • Separate from atherosclerotic PAD; lack of collaterals means rapid tissue loss. Patients should go straight to an emergency department with vascular services, not outpatient imaging (1).
  • Rutherford classification drives urgency and the endovascular vs open choice (2)(3).
Assessment and clinical features

Sudden pain, pallor, coolness, pulse loss, sensory change or weakness; motor/sensory loss indicates threat.

  • The "6 Ps": pain, pallor, pulselessness, poikilothermia (coolness), paraesthesia, paralysis (3).
  • Ask about AF/anticoagulation, previous bypass or stent, claudication history, aneurysm.
  • Examine all pulses, Doppler signals (arterial and venous), capillary refill, sensation (light touch, toes vs beyond) and motor power. Look for a cardiac source and for contralateral signs.
Differentials and investigations

Clinical limb-viability assessment and urgent imaging when it will guide treatment without harmful delay.

  • Rutherford grades (3)(4):
    • I viable: no sensory or motor loss; audible arterial and venous Doppler.
    • IIa marginally threatened: minimal sensory loss (toes), no weakness; arterial Doppler often inaudible, venous audible.
    • IIb immediately threatened: sensory loss beyond toes, mild-moderate weakness; arterial inaudible, venous audible.
    • III irreversible: profound anaesthesia, paralysis (rigor); no arterial or venous signals.
  • Differentials: aortic dissection, DVT/phlegmasia, compartment syndrome, acute-on-chronic ischaemia, spinal cord or peripheral nerve cause, low-flow state.
  • Tests: bloods (FBC, U&E/creatinine, CK, lactate, coagulation, group and hold), ECG for AF, handheld Doppler; CT angiography when it will not delay treatment (2)(4). Do not delay revascularisation in a grade IIb limb for imaging (2).
Management and follow-up

Immediate vascular/senior contact, analgesia and anticoagulation/revascularisation decisions under the acute pathway.

  • Immediate: call vascular surgery; IV analgesia and fluids; start unfractionated heparin unless contraindicated (one US source quotes an 80-100 units/kg bolus then titration to APTT 2-3 times normal) (2).
  • By grade: I - urgent imaging and revascularisation planning; IIa - urgent revascularisation; IIb - emergency revascularisation; III - generally primary amputation (3)(4).
  • Options: catheter-directed thrombolysis or thrombectomy, open embolectomy, bypass or endarterectomy, hybrid. Endovascular preferred for I and IIa; open or hybrid usually favoured for IIb and embolic disease (3)(4).
  • After revascularisation: watch for reperfusion injury (hyperkalaemia, rhabdomyolysis, acidosis, AKI) and compartment syndrome; fasciotomy if suspected. Investigate the source (echo, rhythm monitoring) and start long-term anticoagulation or antiplatelets as directed by the team.
Red flags and clinical pearls

Neurological deficit is time-critical. Do not apply compression or wait for routine Doppler testing.

  • Motor or sensory loss beyond the toes = threatened limb: hours matter; delay increases amputation risk (2).
  • Absent arterial and venous Doppler signals with paralysis suggests irreversible ischaemia; reperfusion may cause life-threatening hyperkalaemia and myoglobinuria.
  • Keep the limb warm and dependent; avoid cooling or elevation.
  • Viva: Rutherford grades, 6 Ps, management by grade, complications of reperfusion.
References
  1. RACGP AJGP 2020: Peripheral artery disease in the lower limbs
  2. AAST: Acute limb ischemia
  3. ESVS 2020 guidelines on acute limb ischaemia
  4. Acute limb ischemia: an update on diagnosis and management (PMC)

Last updated from Sen’s notes on 9 October 2026.