CardiologyTier 2Disease (DEADMAN)

Acute limb ischaemia

Description

Sudden interruption of arterial blood flow to a limb - a vascular emergency, classically the "6 Ps": pain, pallor, pulselessness, paraesthesia, paralysis, poikilothermia (perishingly cold)

Embolic (the majority, often a cardiac source - AF) vs thrombotic (in situ thrombosis on pre-existing atherosclerotic plaque, more insidious onset, often a prior claudication history) vs traumatic

Embolic source - AF (most common), post-MI mural thrombus, valvular disease, aortic aneurysm
Thrombotic - acute plaque rupture/thrombosis on chronic PAD, often less dramatic onset than embolic since collaterals have already developed

Clinical (the 6 Ps) + handheld Doppler to assess pulses/waveform when not palpable
CT angiography defines the level of occlusion and guides intervention planning - but should not delay reperfusion in a threatened limb

Rutherford classification (stage I - viable, no sensory/motor loss - to III - irreversible, non-salvageable) determines urgency and whether revascularisation vs primary amputation is appropriate
Immediate: IV heparin anticoagulation once diagnosis is suspected (unless contraindicated), analgesia
Revascularisation - embolectomy (Fogarty catheter), catheter-directed thrombolysis, or surgical bypass depending on cause/level/urgency
Irreversible ischaemia (stage III, fixed mottling, tense/paralysed limb) -> primary amputation; revascularisation here risks life-threatening reperfusion injury/hyperkalaemia

Time-critical - muscle necrosis begins within ~6 hours of complete ischaemia; delayed reperfusion risks compartment syndrome and reperfusion injury (myoglobinuria, hyperkalaemia, acute kidney injury)

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