Acute Limb Ischaemia
Acute limb ischaemia is a sudden decrease in limb perfusion that causes a time-critical threat to limb viability. Patients who present with two weeks of symptoms of ischaemia are considered to have chronic limb ischaemia (manifested by ischaemic rest pain, ischaemic ulcers and/or gangrene). This pathway deals with acute limb ischaemia.
Acute limb ischaemia may be due to thrombosis, embolism, or rarely dissection. Risk factors
Recent myocardial infarction
Large vessel aneurysmal disease (eg, aortic aneurysm, popliteal aneurysm)
Prior lower extremity revascularization (angioplasty/stent, bypass graft)
Risk factors for aortic dissection
Deep vein thrombosis (paradoxical embolism or phlegmesia)
Step 1: Pathway Entry
Patients with acute arterial occlusion usually present with some of the 6 ‘Ps’: pain, pallor, pulselessness, perishingly cold, paraesthesia and paralysis. Paraesthesia and paralysis from ischaemia indicate a threatened limb that requires emergency surgical review, regardless of the cause.
Step 2: Is the Patient Stable?
Resuscitate if unstable. Damage from an acutely ischaemic limb is exacerbated by hypotension and hypoxia.
Step 3: Focused assessment
Obtain a focused history and examination. In particular, look for symptoms of peripheral arterial disease prior to the onset of the acute limb ischaemia, the presence of atherosclerotic risk factors, which suggest pre-existing thrombosis. Bedside doppler is useful to assess and detect peripheral pulses.
Peripheral pulses should be examined and documented. The intensity is graded 0 to 4+:
- 0 no palpable pulse;
- 1+ a faint, but detectable pulse;
- 2+ diminished pulse;
- 3+ normal pulse; and
- 4+ a bounding pulse.
Bruits (detected by auscultation over the large and medium-sized arteries e.g., carotid, brachial, abdominal aorta, femoral, with the diaphragm of the stethoscope using light to moderate pressure) and the presence of a "thrill" (palpable vibratory sensation over a vessel in which a loud bruit is audible, indicative of marked turbulence in local blood flow suggesting significant vascular pathology) should be noted.
12 lead ECG to look for atrial fibrillation (possible embolic source). Send bloods for FBC, EUC, CK, coagulation, lactate (may be helpful in assessing and tracking the degree of tissue hypoperfusion) and G+S if surgery imminent or possible.
Step 4: Is the Limb Viable?
Not immediately threatened
No sensory loss or weakness
Audible arterial doppler signals
Urgent work up indicated
- Marginally threatened
Salvageable if promptly treated
Minimal sensory loss (toes or none), no weakness
Often inaudible arterial doppler
- Immediately threatened
Salvageable with immediate revascularisation
Sensory loss affecting more than the toes or distal fingers with rest pain
Mild to moderate weakness
Usually inaudible arterial Doppler
Emergency intervention indicated
Major tissue loss and permanent nerve damage inevitable
Profound sensory loss
Inaudible arterial Doppler
Step 5: Diagnosis
Further imaging would be after consultation with the vascular surgeon, and is determined by viability of the limb and availability of imaging modalities. Options include
Angiography in OT
Step 6: Management
Early consultation of vascular surgeon will guide treatment. In the ED treatment would include
Correction of dehydration with IV fluids
Keeping the patient NBM in anticipation of further intervention
Definitive treatment would depend on the viability if the limb, aetiology and location of the lesion, surgical preference and patient suitability for surgery. Peripheral occlusions in a viable limb may be managed by catheter directed thrombolysis, whereas revascularisation of the threatened limb is more time critical. Irreversible changes may occur with 4-6 hours of ischaemia. Surgical options include:
Embolectomy (catheter or open)
Bypass (if arterial thrombosis present)
Treatment of the non-viable limb is amputation.
Further references and resources
BMJ Best Practice - Gangrene
Life in the Fast Lane - A vascular emergency: cool, blotchy legs
Up to date (requires login) - Overview of acute arterial occlusion of the extremities (acute limb ischemia)