A 70-year-old man presents to the ED having developed sudden onset severe pain in his right leg. This occurred whilst he was watching television 1 hour earlier. On examination he is distressed, and his right leg is pale in appearance. His right foot feels cold to touch, there are no palpable foot pulses, and he has reduced sensation in his foot and lower leg.
The most likely diagnosis, in this case, is acute limb ischaemia. Acute limb ischaemia is defined as a sudden decrease in limb perfusion that threatens the viability of the limb. It is most commonly caused by either acute thrombotic occlusion of a previously partially occluded, thrombosed arterial segment or secondary to an embolus from a distant site. It is a surgical emergency, and without surgical revascularisation, complete acute ischaemia results in extensive tissue necrosis within six hours.
The typical features of acute limb ischaemia are classically described using the ‘6 Ps’:
- Pain (constantly present and persistent)
- Pulseless (ankle pulses are always absent
- Pallor (or cyanosis or mottling)
- Power loss or paralysis
- Paraesthesia or reduced sensation or numbness
- Perishing with cold
2. What is the most common cause of this condition?
The most common cause of acute limb ischaemia is acute thrombotic occlusion of a pre-existing stenotic arterial segment (60% of cases). The second commonest cause is embolism (30%), e.g., from left atrial thrombus in patients with atrial fibrillation (accounts for 80% of peripheral emboli), mural thrombus following myocardial infarction, or from prosthetic heart valves. Distinguishing these two conditions is important because treatment and prognosis are different.
Other causes include:
- Raynaud’s syndrome
- Iatrogenic injury
- Popliteal aneurysm
- Aortic dissection
- Compartment syndrome
3. How is this condition managed?
If acute limb ischaemia is suspected, an emergency assessment by a vascular surgeon should be arranged.
Secondary care management will depend on the type of occlusion (thrombosis or embolus), location, duration of ischaemia, co-morbidities, type of conduit (artery or graft), the risks of treatment, and the viability of the limb.
- Percutaneous catheter-directed thrombolytic therapy
- Surgical embolectomy
- Endovascular revascularisation if the limb is viable
- Revascularisation if the limb is marginally or immediately threatened – whether a surgical or endovascular technique is more appropriate will depend on a number of factors including time to revascularisation and the severity of sensory and motor deficits
- Amputation if the limb is unsalvageable (as the revascularization of an irreversibly ischaemic limb with extensive muscle necrosis can lead to reperfusion syndrome from the release of inflammatory mediators and result in multiorgan damage and death).
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