Acute Limb Ischaemia
Sudden occlusion of a previously patent limb artery by embolus or in-situ thrombosis, cutting off perfusion so abruptly that irreversible muscle and nerve damage begins within hours, a surgical emergency defined by the six Ps.
In a nutshell
Sudden arterial occlusion, from embolus or in-situ thrombosis, removes flow abruptly with no time for collaterals to form, so ischaemia is severe and irreversible tissue damage begins within about six hours. The six Ps track that timeline, and revascularisation is a race against the clock.
Classic presentation
A sudden painful, pale, pulseless, cold leg with paraesthesia progressing to paralysis, in a patient with atrial fibrillation (embolic) or known claudication (thrombotic).
Key points
- Embolic occlusion lodges at a bifurcation in a previously healthy artery with no collaterals, so onset is sudden and severe, often with a clear time of onset and no antecedent claudication.
- Thrombotic occlusion occurs on pre-existing atherosclerosis where collaterals have already formed, so onset is often less abrupt, usually with a history of claudication.
- The six Ps represent a worsening timeline, not a simultaneous checklist; sensory then motor loss signals a threatened limb.
- Irreversible muscle and nerve damage begins around six hours after occlusion without adequate collateral flow: treat as a time-critical surgical emergency.
- Reperfusion after revascularisation can cause hyperkalaemia, myoglobinuria, compartment syndrome and acute kidney injury: monitor closely after restoring flow.
- Fixed mottling and paralysis indicate a non-salvageable limb, where primary amputation may be safer than futile revascularisation.
First-line investigation
Immediate clinical assessment with handheld arterial Doppler at the bedside; imaging must never delay urgent referral in a threatened limb.
First-line management
Immediate systemic anticoagulation, resuscitation and emergency vascular surgery referral for revascularisation within hours.
Exam traps
- Absent pulses with a warm, viable-looking limb is not reassuring: check sensory and motor function, which fail before the limb looks obviously dead.
- Do not wait for CT angiography in a hard-signs emergency such as fixed mottling or paralysis; this calls for immediate surgical referral, not imaging first.
- Reperfusion can precipitate life-threatening hyperkalaemia and AKI: anticipate it, do not be surprised by it after 'successful' revascularisation.
Educational content pending clinical review. Not medical advice.